Geothlypis formosa - (Wilson, 1811)
Kentucky Warbler
Other English Common Names: Kentucky warbler
Synonym(s): Oporornis formosus (Wilson, 1811)
Taxonomic Status: Accepted
Related ITIS Name(s): Oporornis formosus (A. Wilson, 1811) (TSN 178937)
French Common Names: Paruline du Kentucky
Spanish Common Names: Chipe Patilludo
Unique Identifier: ELEMENT_GLOBAL.2.103148
Element Code: ABPBX11010
Informal Taxonomy: Animals, Vertebrates - Birds - Perching Birds
 
Kingdom Phylum Class Order Family Genus
Animalia Craniata Aves Passeriformes Parulidae Geothlypis
Genus Size: C - Small genus (6-20 species)
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Concept Reference
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Concept Reference: American Ornithologists' Union (AOU). 1998. Check-list of North American birds. Seventh edition. American Ornithologists' Union, Washington, D.C. [as modified by subsequent supplements and corrections published in The Auk]. Also available online: http://www.aou.org/.
Concept Reference Code: B98AOU01NAUS
Name Used in Concept Reference: Oporornis formosus
Taxonomic Comments: Phylogenetic analyses of sequences of mitochondrial and nuclear DNA (Escalante et al. 2009, Lovette et al. 2010) indicate that several species often placed in Oporornis (tolmiei, philadelphia, and formosa) are more closely related to Geothlypis species than to Oporornis sensu stricto (cf. Lowery and Monroe 1968).
Conservation Status
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NatureServe Status

Global Status: G5
Global Status Last Reviewed: 07Apr2016
Global Status Last Changed: 03Dec1996
Ranking Methodology Used: Ranked by inspection
Rounded Global Status: G5 - Secure
Reasons: Large breeding range in the eastern (mainly southeastern) U.S. but declining in recent decades, due most likely to loss and fragmentation of breeding and/or winter habitat.
Nation: United States
National Status: N5B (19Mar1997)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Alabama (S4B), Arizona (S1M), Arkansas (S4B), Colorado (SNA), Connecticut (S3B), Delaware (S3B), District of Columbia (S3S4N), Florida (S3B), Georgia (S5), Illinois (S5), Indiana (S4B), Iowa (S1B,S3N), Kansas (S3B), Kentucky (S5B), Louisiana (S4B), Maryland (S4B), Massachusetts (S2N), Michigan (SNRN), Minnesota (SNA), Mississippi (S5B), Missouri (S4), Nebraska (S3), New Jersey (S3B,S3N), New York (S2B), North Carolina (S4B), Ohio (S5), Oklahoma (S4B), Pennsylvania (S4B), South Carolina (S4B), Tennessee (S4), Texas (S3B), Virginia (S5), West Virginia (S3B), Wisconsin (S1S2B)

Other Statuses

IUCN Red List Category: LC - Least concern

NatureServe Global Conservation Status Factors

Range Extent: 200,000-2,500,000 square km (about 80,000-1,000,000 square miles)
Range Extent Comments: BREEDING: from southeastern Nebraska, east across central Iowa, southwestern Wisconsin, northeastern Illinois, central Indiana, north-central Ohio, southern Pennsylvania, northern New Jersey, and southeastern New York, to southwestern Connecticut, south to Texas, Gulf Coast to northwestern Florida, central Georgia, and South Carolina, and west to eastern Kansas and central Oklahoma (AOU 1983). NON-BREEDING: tropical zones of southern Veracruz and Oaxaca, through Chiapas, the base of the Yucatan Peninsula, primarily on the Caribbean slope of northern Central America, throughout Costa Rica and Panama, and into northern Colombia and northwestern Venezuela (AOU 1983, McDonald 1998). Uncommon transient through the West Indies; some may overwinter on eastern and southern West Indies islands (McDonald 1998). Birdlife International (2014) estimates the range size to be 1.1 million square kilometers.

Area of Occupancy: >12,500 4-km2 grid cells
Area of Occupancy Comments: Occupancy is based on breeding pair data showing between 100 to 240 birds per square kilometer (McDonald, 2013). With such numbers per square kilometer and an estimated one million or more individuals, the occupany should easily exceed 20,000 square kilometers.

Number of Occurrences: 81 to >300
Number of Occurrences Comments: This species has an extremely large range and population size (Birdlife International, 2014) so it should meet the lower limits of the EO range.

Population Size: >1,000,000 individuals
Population Size Comments: Locally abundant where there is suitable habitat. Breeding Bird Survey data show the Kentucky warbler to be relatively abundant in West Virginia, Arkansas, and Louisiana. Partners in Flight (2013) estimate the number at 2.8 million individuals while National Audubon Society (2014) estimates it at 1.1 million.

Number of Occurrences with Good Viability/Integrity: Many to very many (41 to >125)
Viability/Integrity Comments: Estimate based on estimated number of EOs.

Overall Threat Impact Comments: Probably adversely affected by forest fragmentation. Whitcomb et al. (1981) reported that populations were only 33% of their maximum potential in forests less than 173 acres (70 ha). Nesting was reported in higher densities at distances approaching 200 ft (61 m) from transmission-line corridors (Kroodsma 1982, Chasko and Gates 1982). Pairing success and territory density were examined in populations occupying small (< 140 ha), isolated forest fragments in an agricultural setting and larger (> 500 ha), contiguous forest tracts in central Missouri by Gibbs and Faaborg (1990). Densities did not differ between fragmented (2.1 males per 10 ha) and contiguous sites (1.9 males per 10 ha), and the proportion of paired and unpaired males was identical between the two forest types. Gibbs and Faaborg (1990) suggested two reasons for the lack of sensitivity to forest area. First, the fact that breeding occurs in heavily vegetated creek-bottoms where nests are inconspicuous may alleviate predation pressure. Second, food (herb and shrub invertebrates) is unlikely to be affected by the increased local evaporation rates and decreased soil and litter moisture levels associated with forest area reduction. Loss of tropical forests may also contribute significantly to the regional declines that have been observed in temperate North America. Some declines parallel deforestation in the tropics, and habitat fragmentation on the breeding grounds cannot account completely for these declines. 1980). According to Bent (1953), a common victim of the brown-headed cowbird (MOLOTHRUS ATER); in parts of Pennsylvania, historical records cite the warbler as the commonest victim of the cowbird. More recently, Robinson (1992) documented brood parasitism by cowbirds, although his data, as well as McDonald's in Virginia, indicate that ground-nesters appear to be less susceptible than shrub-nesting species. Of six nests in central Illinois, two were parasitized with an average 0.8 cowbird eggs per nest and an average 3.0 cowbird eggs per parasitized nest (Robinson 1992). In total, three warblers and one cowbird were raised; in no cases were warblers and cowbirds raised together at the Illinois site. At McDonald's Virginia site, the intensity of cowbird parasitism over 14 years has varied annually from 0% to about 15% of the known nests and fledged families. No correlates have been identified, however, to account for this variation (McDonald, unpubl. data). Unlike the Illinois study, in Virginia warblers and cowbirds were raised and fledged together successfully, with no species-specific survival differences. Predation on nests is probably more common than usually realized because the parents simply start re-nesting within a week unless the nest was destroyed very late in the season (McDonald, unpubl. data). Bent (1953) stated that snakes and other prowling predators have been known to rob nests. At McDonald's site in Virginia, about one-fourth of the nests were depredated before fledging. Indirect evidence, including disturbance of the nest cup, and the results of experiments at the same site on artificial nests, suggest that the major predators at this site are small mammals (e.g., eastern chipmunk [TAMIAS STRIATUS]) and medium-sized mammals (raccoon [PROCYON LOTOR], skunk [MEPHITIS MEPHITIS], and opossum [DIDELPHIS VIRGINIANA]). It is not unlikely that snakes and corvids also prey on these nests (McDonald, unpubl. data). The only documented cases of predation on adults include a bizarre report of one being captured and consumed by a box turtle (TERRAPENE CAROLINA) and McDonald's finding remains of a banded female at her nest of four 7-day-old nestlings, also mostly consumed. A medium-sized mammalian predator, such as a raccoon or opossum, common at the Virginia site, were suspected in the latter predation event.

Short-term Trend: Relatively Stable (<=10% change)
Short-term Trend Comments: North American Breeding Bird Survey (BBS) data indicate a nonsignificant decline averaging 0.7% per year, 1966-1989 (Droege and Sauer 1990), a significant decline of 1.26% per year during 1966-1988, and a significant decline of 1.95% per year for 1978-1988; there was a significant population decline in central North America, 1966-1988, and a significant decline in eastern North America, 1978-1988 (Sauer and Droege 1992). A nonsignificant decline of 18% occurred between 1966 and 1993 and a significant decline of 20% occurred from 1984 to 1993 (Price et al. 1995). James et al. (1992) reanalyzed BBS data for the southeastern and south-central U.S. over the period 1966-1987 using an alternative analysis designed especially for BBS data. The Kentucky warbler, which was especially numerous in the Cumberland Plateau, shows a peak and then a decline. Elsewhere in the uplands this species has been in general decline, most apparently so in the Ridge and Valley. Increases in the lowlands are offset by decreases in the highlands; as a result, the overall population in the region has been stable. The latest BBS from 2002 - 2012 show a 1.02% decline over the 11 year period, a decrease of 10% (Sauer, et. al. 2014).

Long-term Trend: Decline of 30-50%
Long-term Trend Comments: The latest BBS from 1996 - 2012 show a 1.08 annual decrease, for a net decrease of 40% over the given time span (Sauer, et. al. 2014). However, overall, population data seem to present a confusing array of increases and decreases, and range expansions and retreats. McDonald (2013) suggests that since about 1980 the continent-wide population of Kentucky Warblers has been slowly decreasing, although local increases and range expansions seem to be occurring. Increasingly, however, second homes and resorts are appearing in areas considered to be the ?core? of the Kentucky Warbler distribution?e.g., Blue Ridge Mtns. and Cumberland Plateau.

Intrinsic Vulnerability: Moderately vulnerable
Intrinsic Vulnerability Comments: Its habit of nesting on the ground (McDonald, 2013) makes this species vulnerable to areas with human-related predators such as rats, cats, and dogs. Its preference for well-developed ground cover and a thick understory in bottomland hardwoods are often prime sites for low-density development (McDonald, 2013).

Environmental Specificity: Moderate. Generalist or community with some key requirements scarce.
Environmental Specificity Comments: This is a forest-dwelling that is considered vulnerable as are most other non-urban/suburban birds that do not tolerate major human disturbances and developments.

Other NatureServe Conservation Status Information

Inventory Needs: Need better estimates of population size range-wide to better assess suitable management techniques (McDonald, 2013).

Protection Needs: Forest management practices that encourage a dense understory and well-developed ground cover should enhance forest stands for this species (Bushman and Therres 1988). Because Kentucky Warblers are tolerant of openings in canopy, harvesting techniques such as group selection, small or narrow clear-cuts, thinning of ?overmature? trees, and selection-cutting are acceptable practices (Crawford et al. 1981). Light timber stand improvement should also be acceptable to Kentucky Warblers. Although species was thought to benefit from selective logging (Whitcomb et al. 1977), numbers actually declined after such practices in Indiana (Adams and Barrett 1976). Clear-cutting temporarily removes habitat for Kentucky Warbler, but regenerating forest may be reoccupied after 6?7 yr in Virginia (Conner and Adkisson 1975, MVM)) (McDonald, 2013).

Distribution
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Global Range: (200,000-2,500,000 square km (about 80,000-1,000,000 square miles)) BREEDING: from southeastern Nebraska, east across central Iowa, southwestern Wisconsin, northeastern Illinois, central Indiana, north-central Ohio, southern Pennsylvania, northern New Jersey, and southeastern New York, to southwestern Connecticut, south to Texas, Gulf Coast to northwestern Florida, central Georgia, and South Carolina, and west to eastern Kansas and central Oklahoma (AOU 1983). NON-BREEDING: tropical zones of southern Veracruz and Oaxaca, through Chiapas, the base of the Yucatan Peninsula, primarily on the Caribbean slope of northern Central America, throughout Costa Rica and Panama, and into northern Colombia and northwestern Venezuela (AOU 1983, McDonald 1998). Uncommon transient through the West Indies; some may overwinter on eastern and southern West Indies islands (McDonald 1998). Birdlife International (2014) estimates the range size to be 1.1 million square kilometers.

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map
NOTE: The maps for birds represent the breeding status by state and province. In some jurisdictions, the subnational statuses for common species have not been assessed and the status is shown as not-assessed (SNR). In some jurisdictions, the subnational status refers to the status as a non-breeder; these errors will be corrected in future versions of these maps. A species is not shown in a jurisdiction if it is not known to breed in the jurisdiction or if it occurs only accidentally or casually in the jurisdiction. Thus, the species may occur in a jurisdiction as a seasonal non-breeding resident or as a migratory transient but this will not be indicated on these maps. See other maps on this web site that depict the Western Hemisphere ranges of these species at all seasons of the year.
Endemism: occurs (regularly, as a native taxon) in multiple nations, but breeds in a single nation

U.S. & Canada State/Province Distribution
United States AL, AR, AZ, CO, CT, DC, DE, FL, GA, IA, IL, IN, KS, KY, LA, MA, MD, MI, MN, MO, MS, NC, NE, NJ, NY, OH, OK, PA, SC, TN, TX, VA, WI, WV

Range Map
Note: Range depicted for New World only. The scale of the maps may cause narrow coastal ranges or ranges on small islands not to appear. Not all vagrant or small disjunct occurrences are depicted. For migratory birds, some individuals occur outside of the passage migrant range depicted. For information on how to obtain shapefiles of species ranges see our Species Mapping pages at www.natureserve.org/conservation-tools/data-maps-tools.

Range Map Compilers: NatureServe, 2002


U.S. Distribution by County Help
State County Name (FIPS Code)
CT Hartford (09003)*, Litchfield (09005)*, New London (09011)*, Windham (09015)*
NE Cass (31025), Dixon (31051), Nemaha (31127), Richardson (31147)
NJ Burlington (34005), Cape May (34009), Cumberland (34011), Hunterdon (34019), Middlesex (34023), Monmouth (34025), Ocean (34029), Sussex (34037), Warren (34041)
NY Bronx (36005), Broome (36007), Cattaraugus (36009), Chautauqua (36013), Chenango (36017), Dutchess (36027), Nassau (36059), Onondaga (36067), Orange (36071), Putnam (36079), Rockland (36087), Suffolk (36103), Ulster (36111), Westchester (36119)
WI Buffalo (55011), Crawford (55023), Dane (55025), Grant (55043), Green (55045), Iowa (55049), Jackson (55053), Jefferson (55055), La Crosse (55063), Monroe (55081), Pepin (55091), Richland (55103), Sauk (55111), Sheboygan (55117), Vernon (55123), Walworth (55127), Washington (55131), Waukesha (55133)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
01 Lower Connecticut (01080205)+*, Farmington (01080207)+*, Shetucket (01100002)+*, Thames (01100003)+*, Housatonic (01100005)+*, Saugatuck (01100006)+
02 Rondout (02020007)+, Hudson-Wappinger (02020008)+, Lower Hudson (02030101)+, Bronx (02030102)+, Hackensack-Passaic (02030103)+, Raritan (02030105)+, Northern Long Island (02030201)+, Southern Long Island (02030202)+, Long Island Sound (02030203)+, Middle Delaware-Musconetcong (02040105)+, Cohansey-Maurice (02040206)+, Mullica-Toms (02040301)+, Chenango (02050102)+, Owego-Wappasening (02050103)+
04 Milwaukee (04040003)+, Seneca (04140201)+
05 Upper Allegheny (05010001)+, Conewango (05010002)+
07 La Crosse-Pine (07040006)+, Black (07040007)+, Lower Chippewa (07050005)+, Coon-Yellow (07060001)+, Grant-Little Maquoketa (07060003)+, Baraboo (07070004)+, Lower Wisconsin (07070005)+, Kickapoo (07070006)+, Crawfish (07090002)+, Sugar (07090004)+, Upper Fox (07120006)+
10 Lewis and Clark Lake (10170101)+, Lower Platte (10200202)+, Tarkio-Wolf (10240005)+, South Fork Big Nemaha (10240007)+
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
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Basic Description: A 13-cm bird (warbler).
General Description: A short-tailed, long-legged warbler. Length 13 cm. Sexes are similar, but black areas are duller or smaller on most females. Bold yellow spectacles separate black crown from black on face and sides of neck; underparts are entirely yellow, upperparts bright olive.

VOCALIZATIONS: Song is a series of rolling musical notes: "churry churry churry" with each "churry" repeated about six times, much like the song of the Carolina wren (THRYOTHORUS LUDOVICIANUS), but lower in pitch. Primary call is a low, sharp "chuck" (NGS 1987); other calls are used infrequently (McDonald, pers. obs.). See Morton and Young (1986) and Tsipoura and Morton (1988) for information on song.

NEST: cup of grasses, plant fibers, rootlets built on a bulky foundation of dead leaves 10.2-15.2 cm deep; lined with rootlets, weed stalks, grasses (De Garis 1936). Built on or just above the ground at the foot of a tree or shrub, or low in understory vegetation; nest usually is hidden by overhanging vegetation or fallen branches (Harrison 1978).

EGGS: average size 18.6 x 14.3 mm; short-oval to long-oval; shell smooth, has slight gloss; white, creamy white in color, and blotched, dotted, spotted with grays, browns, usually concentrated at large end.

Diagnostic Characteristics: Adults are easily distinguished from other species. Nests are like those of the golden-winged warbler (VERMIVORA CHRYSOPTERA), but unlike many ground-nesting birds, the Kentucky warbler usually builds a nest slightly above ground level (Harrison 1975).
Reproduction Comments: Eggs are laid mainly in May-June. Clutch size is 3-6 (usually 4-5). Incubation lasts 12-13 days, by female. Young are tended by both parents, leave nest at 8-10 days (before they can fly), fed by adults for up to 17 days more. Typically one brood, but sometimes two (Harrison 1975). A first clutch size of 4.12 eggs with 1-2 broods per year and a reproductive effort of 6.18 was reported by Whitcomb et al. (1981) in Maryland.
Ecology Comments: POPULATION DENSITY: Published information on densities from breeding bird censuses in the southeastern U.S. between 1947 and 1979 were summarized by Hamel et al. (1982): mean (se) density was 4.8 (0.56) pairs per 40 ha with a range of 1-8.5 pairs per 40 ha. In Missouri, density was 1.82 males per 10 ha in continuous forest, 0.91-1.29 per 10 ha in isolated forest fragments (Wenny et al. 1993). Wenny et al. (1993) studied two forest fragments, one smaller (300 ha) and one larger (> 800 ha) in Missouri. Kentucky warblers were found to have significantly higher densities in the larger forest area than in both fragments. In the largest contiguously forested site (> 800 ha), the estimated total population size was 243 birds with 98 breeding pairs. Gibbs and Faaborg (1990) found an average 2.2 males per 10 ha in larger forest tracts compared with 1.4 males per 10 ha in smaller fragments. Whitcomb et al. (1981) reported a territorial density of 36 males per sq km in Maryland. In Virginia, densities of 30-55 pairs were observed over the years 1988-1997 in the 1200 ha core area of suitable habitat at the study site (McDonald 1998). Winter density was up to 5.5 birds per 10 ha in Panama, around 30 per 10 ha in Veracruz, Mexico (Mabey and Morton 1992).

TERRITORY SIZE: Territory sizes were found to differ significantly between forest tracts of different size by Wenny et al. (1993): territories averaged 0.8 ha in a large forest (> 800 ha) and 1.08 ha in two smaller fragments (300 ha). In Virginia, territory sizes ranged from about 0.8 to 2 ha; for nearly all territories considered individually, configuration (boundaries) and size remained nearly constant over the 14-year study. With few exceptions, the same male returned to and occupied a given territory for as long as he lived, although returning females did shift from year to year (McDonald, unpubl. data). Territorial in winter (Stiles and Skutch 1989, Mabey and Morton 1992). Individuals commonly return to the same winter territory in successive years (Rappole and Warner 1980).

Non-Migrant: N
Locally Migrant: N
Long Distance Migrant: Y
Mobility and Migration Comments: Arrives in Costa Rica early to mid-September, departs by late April (Stiles and Skutch 1989). Present in South America mostly October-March (Ridgely and Tudor 1989). See also McLaren (1981) and Moore (1990).
Palustrine Habitat(s): FORESTED WETLAND, Riparian
Terrestrial Habitat(s): Forest - Hardwood, Shrubland/chaparral, Woodland - Hardwood
Habitat Comments: BREEDING: Humid deciduous forest (Hamel 1992), dense second growth, swamps. Occurs in stands of various ages but is most common in medium-aged forests (Shugart et al. 1978). Prefers forests with a slightly open canopy, dense understory, and well-developed ground cover (Bushman and Therres 1988). Seldom found in conifers. In Virginia, McShea et al. (1995) found that forest type, streams, and the density of deer were significant variables in territory selection, but forest age (within a reasonable span of years) and the presence of a habitat boundary did not contribute significantly. Specifically, warblers selected cove hardwoods and avoided oak/hickory overstory. The avoidance of oak/hickory overstory is surprising, since a nonquantified gestalt impression of distribution at this site would at first suggest they prefer oak/hickory. Areas with streams and low white-tailed deer (ODOCOILEUS VIRGINIANUS) density also were selected.

NON-BREEDING: In migration, habitats include forest, woodland, scrub, and thickets. In winter, habitat includes the floor of rain forests; also second growth, forest edge, undergrowth (AOU 1983, Bushman and Therres 1988). This species was found in wet forest (most commonly), moist forest (less commonly), and dry forest (rarely) on the Yucatan Peninsula (Lynch 1992); birds were also captured in mid-successional Acahual habitat. From studies in various Latin American countries, Robbins et al. (1992) concluded that wintering birds are ground foragers that require forest. Some birds were found in early successional habitats, but only an occasional bird was captured in pine woods or agricultural habitats. In Belize, found to prefer broadleaved forest edge and interior habitats (Petit et al. 1992).

Adult Food Habits: Invertivore
Immature Food Habits: Invertivore
Food Comments: Walks rapidly over ground overturning leaves with bill, searches under sticks and in crevices, leaps up to snatch insect or spider from overhanging leaf or branch (Terres 1980). In winter in Mexico, gleans insects from the undersurfaces of low herbaceous growth typical of dense humid forests; sometimes climbs into low vegetation; uncommonly takes food items from forest floor (Rappole and Warner 1980). Also forages along twigs in low shrubbery (Stiles and Skutch 1989). Regularly attends army ant swarms in Panama (Ridgely and Tudor 1989).
Adult Phenology: Diurnal
Immature Phenology: Diurnal
Length: 13 centimeters
Weight: 14 grams
Economic Attributes Not yet assessed
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Management Summary
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Stewardship Overview: Primarily a southeastern bird, has shown signs of expanding northward and can now be found at scattered northern localities in Connecticut, New York, and Wisconsin. Prefers rich, moist deciduous forests; bottomland hardwoods and woods near streams are ideal as long as they have a dense hardwood understory. Being a ground-nester, requires well-developed ground cover, and a thick understory is essential. Because of this key requirement, preserve managers should promote dense low vegetation by controlling deer populations. Studies of forest fragmentation in Missouri indicate that preserves should be at least 500 ha in size, and preferably larger. Contiguous forest is ideal since rates of brood parasitism by cowbirds and nest predation by raccoons, jays, opossums, etc., will be lower. In probable global decline; this decline may be more drastic in some regions (e.g., Ridge and Valley, Blue Ridge Mountains, Cumberland Plateau) than in others (e.g., Mississippi Alluvial Plain, Upper Coastal Plain). Tropical deforestation may be one major factor impacting this species.
Restoration Potential: Currently not in need of restoration or recovery. Should the species continue to decline, restoration and recovery seems highly plausible if the correct habitat is provided. Controlling deer populations seems key to developing the dense understories required by this species. Where the species is of most concern (e.g., Connecticut, New York, and Wisconsin), it is on the northern periphery of its range and never has been a common breeder.
Preserve Selection & Design Considerations: Relatively little has been published about the specific habitat and minimum area requirements of this species. It seems reasonable that preserves should be no smaller than 500 ha, and as with most similar species, the larger the better to reduce rates of cowbird parasitism and nest predation. Data from on-going research and a paper in review, both based on a long-term study site in Virginia, however, are available. This study and other observations suggest that preserves must be in deciduous forest with an abundant hardwood understory layer, of about 40-80 years old. Bottomland hardwood forests with little or no slope are favored, and conifer must be avoided. Deer numbers should be controlled (McShea et al. 1995).

Breeding occurs most often in large tracts of forest but may nest in forest patches as small as a few hectares if habitat conditions are suitable. Lynch and Whigham (1982) found that stand size was the most important forest characteristic determining presence in upland forests on Maryland's Coastal Plain. Estimates of minimum area requirements vary. Robbins (1979, 1980) estimated the minimum forest area required to sustain a viable breeding population at 80-125 acres (32-50 ha). Blake and Karr (1984) found warblers breeding in forest islands as small as 6 acres (2.5 ha) in Illinois. Anderson and Robbins (1981) detected breeding in woodlots as small as 20-47 acres (8-19 ha), but found the highest frequency of occurrence in forests 325-4250 acres (130-700 ha). Wenny et al. (1993) found warblers in Missouri to be significantly more abundant in large forest tracts (> 800 ha) compared with two 300-ha fragments; this species was present, but not breeding, on a 340-ha forest fragment, which suggests that forests larger than 300 ha are required (cf. Hayden et al. 1985, and earlier references). Gibbs and Faaborg (1990) did not find differences in densities between fragmented (9-140 ha; 2.1 males per 10 ha) and contiguous (> 500 ha; 1.9 males per 10 ha) sites in central Missouri. Furthermore, the proportion of paired and unpaired males was identical for all forest types. In general, suggested to be less area-sensitive than other ground-nesting Neotropical migrant warblers such as ovenbirds (SEIURUS AUROCAPILLUS) (Blake 1983, Hayden et al. 1985, Gibbs 1988).

Management Requirements: Among six species that clearly need management and/or monitoring attention in the Coastal Plain of the southeastern U.S. (Hunter, unpubl. data). Bushman and Therres (1988) provided the following management guidelines. Forest management practices that encourage a dense understory and well-developed ground cover should enhance forest stands for this species. Because these birds are tolerant of openings in the canopy, harvesting techniques such as group selection, small or narrow clearcuts, thinning of "overmature" trees, and selection cutting are acceptable practices (Crawford et al. 1981). Light timber stand improvement should also be acceptable. Whereas Whitcomb et al. (1977) suggested that this warbler should benefit from selective logging, Adams and Barrett (1976) reported a decline after such practices in Indiana. Clearcutting temporarily removes habitat, but regenerating forest may be reoccupied after a few years. For example, Conner and Adkisson (1975) found birds breeding in a seven-year-old clearcut in Virginia.
Monitoring Requirements: Continuing annual surveys of suitable habitat and known populations using point counts and spot-mapping techniques are probably the most efficient ways to monitor this species. However, even conscientious, season-long application of these techniques will miss some breeding birds, and may also lead to erroneous conclusions about the suitability of the censused area for actually reproducing birds (Gibbs and Faaborg 1990, Gibbs and Wenny 1993, McDonald unpubl. data). Research on the relation of singing behavior as a tool in population estimation is a portion of larger studies in Missouri by John Faaborg and in Virginia by Victoria McDonald, and is an example of the kind of research that is required. Studies that monitor breeding productivity over the years will provide critical information on factors affecting reproductive success and population recruitment and dynamics. It is imperative that we determine why breeding success and numbers of birds may vary.

Gibbs (1988) found unmated males to sing more than five times as often as paired males. This behavior poses obvious difficulties for researchers using counts of singing males to obtain estimates of absolute densities. The bias introduced by unmated males into population counts can potentially yield the impression that less suitable habitats are more preferred. Also, unmated males singing in suboptimal small forest fragments may give the impression that such fragments are suitable for breeding (Gibbs 1988, Gibbs and Wenny 1993).

Management Research Needs: Research priorities on the breeding grounds should be assessment of minimum area requirements and quantification of specific habitat requirements, especially of nest sites, as related to breeding success. In addition, research is needed on determining minimum viable population sizes and the impacts of forest fragmentation (including its effect on predation and cowbird parasitism). On the wintering grounds, similarly, quantification of specific habitat requirements and minimum area requirements should be a top priority. Habitat requirements for the birds in migration should also be addressed.

McDonald's data from banding records during the breeding season have shown that plumage characters, particularly the relative blackness of the crown, is not as reliable a sexing criterion as previously reported (e.g., Bent 1953, Pyle et al. 1987). The accumulation and publication of sex- and age-specific plumage and morphometric data should aid in any research and management requiring information on relative numbers of males and females, including studies on wintering and migratory stop-over grounds.

Biological Research Needs: 3. Determine relationship between breeding habitat type, management practice, and post-fledging survival.The most important research needs are those related to the monitoring and management of the species. Continuing annual surveys of suitable habitat and known populations using point counts and spot-mapping techniques are probably the most efficient ways to monitor this species. MVM?s unpublished data, however, suggest that even conscientious, season-long application of these techniques misses some breeding birds, and may also lead to erroneous conclusions about the suitability of the censused area to birds actually reproducing (Gibbs and Faaborg 1990, Gibbs and Wenny 1993).Management research priorities on the breeding grounds should be the assessment of minimum area requirements, and quantification of specific habitat requirements, especially of nest sites, as related to breeding success. In addition, research is needed to determine minimum viable population sizes and the impacts of forest fragmentation (including its effect on predation and cowbird parasitism). On the wintering grounds, all aspects of life need investigation, especially quantification of specific habitat requirements and minimum area requirements. Habitat requirements for migrating individuals should also be addressed.Other research needs have been alluded to in this account?e.g., the validity of using counts of singing birds to estimate population size, and the correlation between counts of singing males and actual productivity (McDonald, 2013).
Population/Occurrence Delineation
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Group Name: Passerines

Use Class: Breeding
Subtype(s): Foraging Area, Nest Site, Nesting Colony
Minimum Criteria for an Occurrence: Evidence of historical breeding, or current and likely recurring breeding, at a given location, minimally a reliable observation of one or more breeding pairs in appropriate habitat. Be cautious about creating EOs for observations that may represent single breeding events outside the normal breeding distribution.

Mapping Guidance: Breeding occurrences include nesting areas as well as foraging areas.

For swallows and other species that have separate nesting and foraging areas, separations are based on nest sites or nesting areas, not to locations of foraging individuals. For example, nesting areas separated by a gap larger than the separation distance are different occurrences, regardless of the foraging locations of individuals from those nesting areas. This separation procedure is appropriate because nesting areas are the critical aspect of swallow breeding occurrences, tend to be relatively stable or at least somwhat predictable in general location, and so are the basis for effective conservation; foraging areas are much more flexible and not necessarily static.

Separation Distance for Unsuitable Habitat: 5 km
Separation Distance for Suitable Habitat: 5 km
Separation Justification: Significant dispersal and associated high potential for gene flow among populations of birds separated by tens of kilometers (e.g., Moore and Dolbeer 1989), and increasing evidence that individuals leave their usual home range to engage in extrapair copulations, as well as long foraging excursions of some species, make it difficult to circumscribe occurrences on the basis of meaningful population units without occurrences becoming too large. Hence, a moderate, standardized separation distance has been adopted for songbirds and flycatchers; it should yield occurrences that are not too spatially expansive while also accounting for the likelihood of gene flow among populations within a few kilometers of each other.

Be careful not to separate a population's nesting areas and foraging areas as different occurrences; include them in the same occurrence even if they are more than 5 km apart. Mean foraging radius (from nesting area) of Brown-headed Cowbird females was 4.0 kilometers in California, 1.2 kilometers in Illinois-Missouri (Thompson 1994). Yellow-headed Blackbirds, Brewer's Blackbirds, and probably Red-winged Blackbirds all forage up to 1.6 kilometers away from breeding colony (Willson 1966, Horn 1968). In one study, Brewer's Blackbirds were found as far as 10 kilometers from nesting area (Williams 1952), but this may be unusual.

For swallows and other parrerines with similar behavioral ecology, separation distance pertains to nest sites or nesting colonies, not to locations of foraging individuals. For example, nesting areas separated by a gap of more than 5 km are different occurrences, regardless of the foraging locations of individuals from those nesting areas. This separation procedure is appropriate because nesting areas are the critical aspect of swallow breeding occurrences, tend to be relatively stable or at least somwhat predictable in general location, and so are the basis for effective conservation; foraging areas are much more flexible and not necessarily static.

Be cautious about creating EOs for observations that may represent single breeding events outside the normal breeding distribution.

Unsuitable habitat: Habitat not normally used for breeding/feeding by a particular species. For example, unsuitable habitat for grassland and shrubland birds includes forest/woodland, urban/suburban, and aquatic habitats. Most habitats would be suitable for birds with versatile foraging habits (e.g., most corvids).

Date: 10Sep2004
Author: Hammerson, G.

Use Class: Migratory stopover
Subtype(s): Foraging Area, Roost Site
Minimum Criteria for an Occurrence: For most passerines: Evidence of recurring presence of migrating individuals (including historical) and potential recurring presence at a given location; minimally a reliable observation of 25 birds in appropriate habitat.

For swallows: Evidence of recurring presence of migrating flocks (including historical) and potential recurring presence at a given location; minimally a reliable observation of 100 birds in appropriate habitat (e.g., traditional roost sites).

Occurrences should be locations where the species is resident for some time during the appropriate season; it is preferable to have observations documenting presence over at least 7 days annually.

EOs should not be described for species that are nomadic during nonbreeding season: e.g., Lark Bunting.

Be cautious about creating EOs for observations that may represent single events.

Separation Distance for Unsuitable Habitat: 5 km
Separation Distance for Suitable Habitat: 5 km
Separation Justification: Separation distance somewhat arbitrary but intended to define occurrences of managable size for conservation purposes. Occurrences defined primarily on the basis of areas supporting concentrations of birds, rather than on the basis of distinct populations.

For swallows and other species with similar behavioral ecology, the separation distance pertains to communal roost sites rather than to foraging areas; the former tend to be more stable and specific over time than the latter.

Date: 03Sep2004
Author: Hammerson, G., and S. Cannings

Use Class: Nonbreeding
Subtype(s): Foraging Area, Roost Site
Minimum Criteria for an Occurrence: Any area used traditionally in the nonbreeding season (used for populations that are not resident in a location year-round). Minimally, reliable observations of 10 or more individuals in appropriate habitat for 20 or more days at a time. For G1-G3 species, observations of fewer individuals could constitute an occurrence of conservation value. Sites used during migration should be documented under the 'migratory stopover' location use class.

Separation Distance for Unsuitable Habitat: 5 km
Separation Distance for Suitable Habitat: 5 km
Separation Justification: Separation distance is necessarily arbitrary but attempts to balance the high mobility of birds with the need for occurrences of reasonable spatial scope. Note that a population's roost sites and foraging areas are parts of the same occurrence, even if they are more than 5 km apart.

For swallows and other species with similar behavioral ecology, the separation distance pertains to communal roost sites rather than to foraging areas; the former tend to be more stable and specific over time than the latter.

Date: 03Sep2004
Author: Hammerson, G.

Use Class: Nonmigratory
Minimum Criteria for an Occurrence: Occurrences are based on evidence of historical presence, or current and likely recurring presence, at a particular location. Such evidence minimally includes collection or reliable observation and documentation of one or more individuals in or near appropriate habitat.

These occurrence specifications are used for nonmigratory populations of passerine birds.

Separation Barriers: None.
Separation Distance for Unsuitable Habitat: 5 km
Separation Distance for Suitable Habitat: 5 km
Separation Justification: Significant dispersal and associated high potential for gene flow among populations of birds separated by tens of kilometers (e.g., Moore and Dolbeer 1989), and increasing evidence that individuals leave their usual home range to engage in extrapair copulations, as well as long foraging excursions of some species, make it difficult to circumscribe occurrences on the basis of meaningful population units without occurrences becoming too large. Hence, a moderate, standardized separation distance has been adopted for songbirds and flycatchers; it should yield occurrences that are not too spatially expansive while also accounting for the likelihood of gene flow among populations within a few kilometers of each other.

Be careful not to separate a population's nesting areas and breeding-season foraging areas as different occurrences; include them in the same occurrence even if they are more than 5 km apart. Blue jays have small summer home ranges but fly up to 4 kilometers to harvest mast (Tarvin and Woolfenden 1999). Flocks of pinyon jays range over 21-29 square kilometers (Ligon 1971, Balda and Bateman 1971); nesting and foraging areas may be widely separated. Tricolored blackbirds forage in flocks that range widely to more than 15 kilometers from the nesting colony (Beedy and Hamilton 1999).

Unsuitable habitat: Habitat not normally used for breeding/feeding by a particular species. For example, unsuitable habitat for grassland and shrubland birds includes forest/woodland, urban/suburban, and aquatic habitats. Most habitats would be suitable for birds with versatile foraging habits (e.g., most corvids).

Date: 10Sep2004
Author: Hammerson, G.
Notes: These specs pertain to nonmigratory species.
Population/Occurrence Viability
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U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
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Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 18Nov2014
NatureServe Conservation Status Factors Author: Dirrigl, F., Jr., G. Hammerson, and R. Sallabanks; Modified by Jue, Dean K.
Management Information Edition Date: 08Oct1993
Management Information Edition Author: SALLABANKS, R., AND M.V. MCDONALD; REVISIONS BY D.W. MEHLMAN
Management Information Acknowledgments: We thank Sarah Mabey and John Faaborg for sending unpublished data, preprints, and reprints. Thanks also go to all Heritage biologists who responded to the ESA questionnaire: Alabama - Mark Bailey; Connecticut - Dawn McKay; Delaware - Christopher Heckcher; Florida - Steve Jones; Georgia - Jon Ambrose; Illinois - Vernon Kleen; Indiana - John Castrale and Michelle Martin; Kansas - Bill Busby; Kentucky - Brainard Palmer- Ball; Louisiana - Steve Schively; Maryland - Lynn Davidson; Missouri - Brad Jacobs; Mississippi - Tom Mann; North Carolina - Harry LeGrand, Jr.; Nebraska - Mary Clausen; New Jersey - Rick Dutko; New York - Kathy Schneider; Ohio - Daniel Rice; Pennsylvania - Barb Barton; Rhode Island - Rick Enser; South Carolina - John Cely; Tennessee - Paul Hamel and Andrea Shea; Virginia - Sarah Mabey; and West Virginia - Barbara Sargent. Judith Soule of the Michigan Natural Features Inventory provided valuable advice on writing the ESA, Bruce Peterjohn of the U.S. Fish and Wildlife Service, Office of Migratory Bird Management, Patuxent Wildlife Research Center sent BBS data, and Melissa Morrison of The Nature Conservancy's Eastern Regional Office sent ELLINK reports.
Element Ecology & Life History Edition Date: 11Apr1996
Element Ecology & Life History Author(s): SALLABANKS, R., M. V. MCDONALD, AND G. HAMMERSON

Zoological data developed by NatureServe and its network of natural heritage programs (see Local Programs) and other contributors and cooperators (see Sources).

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  • Robbins, C.S. 1980. Effect of forest fragmentation on breeding bird populations in the Piedmont of the mid-Atlantic region. Atlantic Naturalist: pp. 31-36.

  • Robinson, S. K. 1992. Population dynamics of breeding neotropical migrants in a fragmented Illinois landscape. Pages 408-18 in J. M. Hagan III and D. W. Johnston (editors). Ecology and Conservation of Neotropical Migrant Landbirds. Smithsonian Institution Press, Washington, D.C.

  • Sauer, J. R., J. E. Hines, J. E. Fallon, K. L. Pardieck, D. J. Ziolkowski, Jr., and W. A. Link. 2014. The North American Breeding Bird Survey, Results and Analysis 1966 - 2012. Version 02.19.2014. USGS Patuxent Wildlife Research Center, Laurel, MD. http://www.pwrc.usgs.gov/.

  • Sauer, J. R., J. E. Hines, J. E. Fallon, K. L. Pardieck, D. J. Ziolkowski, Jr., and W. A. Link. 2014. The North American Breeding Bird Survey, Results and Analysis 1966 - 2012. Version 02.19.2014 USGS Patuxent Wildlife Research Center, Laurel, MD.
     

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  • See SERO listing

  • Shugart, H. H., T. M. Smith, J. T. Kitchings, and R. L. Kroodsma. 1978. The relationship of nongame birds to southern forest types and successional stages. Pages 5-16 in R. M. DeGraaf (editor). Management of southern forests for nongame birds. U.S. Forest Service General Technical Report SE-14.

  • Sibley, C.G., and B.L. Monroe, Jr. 1990. Distribution and Taxonomy of Birds of the World. Yale University Press, New Haven, CT. xxiv + 1111 pp.

  • Sibley, D. A. 2000a. The Sibley guide to birds. Alfred A. Knopf, New York.

  • Stevenson, H.M., and B.H. Anderson. 1994. The Birdlife of Florida. University Press of Florida, 891 pp.

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  • Tarvin, K. A., and G. E. Woolfenden. 1999. Blue Jay (Cyanocitta cristata). No. 469 IN A. Poole and F. Gill, editors. The birds of North America. The Birds of North America, Inc., Philadelphia, PA. 32pp.

  • Terres, J. K. 1980. The Audubon Society encyclopedia of North American birds. Alfred A. Knopf, New York.

  • Thompson, F. R., III. 1994. Temporal and spatial patterns of breeding brown-headed cowbirds in the midwestern United States. Auk 111:979-990.

  • Tsipoura, N., and E. S. Morton. 1988. Song-type distribution in a population of Kentucky warblers. The Wilson Bulletin 100:9-16.

  • Wenny, D. G., et al. 1993. Population density, habitat selection and minimum area requirements of three forest-interior warblers in central Missouri. Condor 95:968-979.

  • Whitcomb, B. L., R. F. Whitcomb, and D. Bystrak. 1977. Long-term turnover and effects of selective logging on the avifauna of forest fragments. American Birds 31:17-23.

  • Whitcomb, R. F., C. S. Robbins, J. F. Lynch, B. L. Whitcomb, M. K. Klimciewicz, and D. Bystrak. 1981. Effects of forest fragmentation on avifauna of the eastern deciduous forest. Pages 125-206 in R. L. Burgess, and B. L. Sharpe (editors). Forest island dynamics in man-dominated landscapes.

  • Williams, L. 1952b. Breeding behavior of the Brewer blackbird. Condor 54:3-47.

  • Willson, M. F. 1966. Breeding ecology of the Yellow-headed Blackbird. Ecological Monographs 36:51-77.

  • Zook, J. L. 2002. Distribution maps of the birds of Nicaragua, Costa Rica, and Panama. Unpublished.

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