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Birds of Maryland and The District of Columbia

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... Historical studies from around the turn of the 20 th Century considered Longeared Owls to be "uncommon" or "resident" on the Delmarva Peninsula despite more abundant concealing habitat and fewer observers to detect owls relative to more modern times (Rives 1890, Kirkwood 1895, Pennock 1904, Rhoads and Pennock 1905. Conversely, studies during the mid-20 th Century classified the species status as "rare" (Hampe and Kolb 1947, Murray 1952, Stewart and Robbins 1958. Later studies associated the perceived less frequent detection and/or population decline to a mid-century surge in Great Horned Owl (Bubo virginianus) and Red-tailed Hawk (Buteo jamaicensis) populations (Bosakowski et al. 1989, Hess et al. 2000. ...
... Historically, the Long-eared Owl was listed as "resident" in Delaware (Rhoads and Pennock 1905) and Virginia (Rives 1890), and "resident, but…not common" and "rare permanent resident" in Maryland (Kirkwood 1895, Hampe andKolb 1947) which implies potential nesting on the Delmarva Peninsula. Regional studies since the first half of the 20 th Century (Murray 1952, Stewart and Robbins 1958, Hess et al. 2000, Rottenborn and Brinkley 2007, Ellison 2010) restrict any potential nesting in those jurisdictions to Piedmont or higher elevations north, south, or west of the Coastal Plain peninsula. Nesting was documented just 3 km (2 mi) east of the Delmarva Peninsula on the New Jersey Coastal Plain near Salem (Stone 1965); 13 km (8 mi) north on the Delaware Piedmont north of Wilmington (B.C. ...
... Nesting was documented just 3 km (2 mi) east of the Delmarva Peninsula on the New Jersey Coastal Plain near Salem (Stone 1965); 13 km (8 mi) north on the Delaware Piedmont north of Wilmington (B.C. Hiatt in Potter 1937), and 52 km (32 mi) west on the Maryland Piedmont near Baltimore (Kirkwood 1895, Kolb 1947a, Kolb 1947b, Stewart and Robbins 1958 (Stewart and Robbins 1958, Marks et al. 1994, Ellison 2010) and subsequent egg-laying, incubation, and brooding of nestlings could have been completed by May and thereafter exhibit no physical signs of nesting. An owl reported on 14 September 1941 near the center of the peninsula suggests a resident or unusually early southbound migrant. ...
Article
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We determined the occurrence distribution, annual frequency, and seasonal chronologies of Long-eared Owls (Asio otus) on the Delmarva Peninsula using various types of records from 1941 through 2016. Records were distributed throughout the peninsula with annual peak frequencies fluctuating in a general 3–5-year periodicity. Seasonal records occurred in three periods where the frequency increased and subsequently decreased. An early-March to mid- April period approximating northbound migrants peaked on 19 March (±3.2 SEM), a late-October to mid-December period approximating southbound migrants peaked on 14 November (±2.4 SEM), and a late-November to late- March winter period peaked on 12 January (±2.6 SEM). Historically there is no record of nesting on the peninsula, nor was it confirmed among the few spring and summer records in this study. The Long-eared Owl is a poorly understood species with little to nothing known about it regionally. This study provides some valuable insights to their life history on the Delmarva Peninsula, a more definitive status than that given for the region in the literature, and furnishes baseline information for future study.
... In Maryland, Stewart and Robbins (1958) considered Swainson's Warbler an uncommon breeder in swamp habitats along the Pocomoke River and its tributaries and rare elsewhere in other "stream swamps" in Worcester County. Boone (1984, 1985), in a review of Maryland's rare, threatened, and endangered bird species, regarded Swainson's Warbler as highly rare, noting that no more than 10 pairs have ever been found in Maryland. ...
... At the time, it was assumed that this was a vagrant spring migrant because the nearest known breeding site was Dismal Swamp, about 160 km to the south along the Virginia-North Carolina border (Vaughn and Robbins 1996). After the initial report, Swainson's Warbler was regularly found at Great Cypress Swamp for many years (e.g., Heckscher 2000;Hess et al. 2001;Kleen 1965;Robbins 1950Robbins , 1959Robbins and Boone 1984;Springer and Stewart 1948;Stewart and Robbins 1958;Vaughn and Robbins 1996). Table 1 details the published observations of this species from Great Cypress Swamp including one of the only confirmed nest records from the peninsula. ...
... Swainson's Warbler was first reported from Hickory Point Swamp on 2 May 1946 by Stewart and Robbins (1947), who observed two pairs and collected one specimen. Since 1946, the species has been reported only periodically (Table 1; Meanley 1950Meanley , 1971Robbins and Boone 1984;Stewart and Robbins 1958;Vaughn and Robbins 1996). Bennett et al. (1999) estimated that Swainson's Warbler occupied approximately 4.2% of the 900-ha swamp (30 ha) based on surveys conducted on 10 June 1997 at 26 randomly placed point count stations. ...
Article
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Swainson's Warbler is among the forest-bird species of highest conserva-tion concern in the eastern United States. Recent publications include conflicting accounts of the species' breeding status at the northern limit of its range on the Delmarva Peninsula in Maryland and Delaware. To clarify this ambiguity, we re-viewed and compiled the peninsula's published locality records. Three conclusions are evident from our analysis: 1) despite reports to the contrary, Swainson's Warbler continues to persist in two disjunct areas within the Pocomoke River watershed: Great Cypress Swamp in Maryland and Delaware, and Hickory Point Swamp in Worcester County, MD; 2) sporadic breeding-season records suggest small scattered breeding sites in other parts of the watershed, especially in the upper Nassawango Creek in Wicomico County, MD; and 3) further effort is warranted to better identify and delineate regularly occurring breeding areas in unexplored areas of the Pocomoke and adjacent Nanticoke watersheds. Because the long-term viability of the peninsula's population is uncertain, we believe the species' current legal status as State Endangered in Maryland and Delaware remains warranted.
... In the Gunpowder River area at the head of Chesa¬ peake Bay, the Seaside Sparrow has been recorded in 3 years, between the extreme dates of 21 April and 10 June (Stewart and Robbins 1958), and there has been one spring sighting near the upper limit of tidewater in the Potomac River at Dyke Marsh in Fairfax County, Virgin¬ ia (Scott and Cutler 1975). ...
... A detailed map of estimated breeding range in Chesapeake Bay is shown in Figure 2. Range in the southern portion of the Bay is based on unpublished field notes of H. H. Bailey, who charted distribution of marshes suitable for Clapper Rails in 1915: most of the same marshes would be suitable for nesting Seaside Sparrows. Data for the northern half of the Bay are from F. R. Scott, H. T. Armistead, the Somerset and Balti¬ more County Breeding Bird Atlases of the Maryland Ornithological Society, and the breeding range as mapped byStewart and Robbins (1958), updated by more recent observations from members of the Mary¬ land Ornithological Society.A. m. macgillivraii. Coastal and brackish marshes from Dare County in northeastern North Carolina south into Camden County in extreme southeastern Georgia.A. m. pelonota. ...
... Historically, this species bred throughout the mid-Atlantic Coastal Plain (Jackson 1978). As recently as the 1930's and 1940's resident birds were known from the open maritime forests of Maryland (Meanley 1943, Stewart andRobbins 1958). Since that time, the range has contracted to southeastern Virginia as northern breeding sites have been lost. ...
... In Illinois, 56 ha has been reported as a minimum area requirement (Herkert 1994). Although found regularly in open grasslands earlier in this century (Robbins and Stewart 1958), this species has disappeared from such habitats over the past 30 years. No recent records within this physiographic region report the use of grassland habitats. ...
... Similar patterns of displacement have been reported throughout the Chesapeake Bay region. In Maryland, records suggest king rails were fairly common in tidal wetlands until the 1980s (Blom et al., 1996;Stewart & Robbins, 1958) but declined precipitously by the 1990s (Brinker et al., 2002). This decline coincided with increased abundance and spread of clapper rails (Brinker et al., 2002). ...
... In this scenario, neutral DNA from king rails percolate into the clapper genome through limited hybridization and diffuse through the porous species boundary because these markers are invisible to selection. However, when taking into consideration the documented salinity changes (Church & White, 2006;Jarrell et al., 2016), species' occupancy patterns at other brackish marshes in the Chesapeake Bay watershed (Blom et al., 1996;Brinker et al., 2002;Stewart & Robbins, 1958), and the "wave-front" model of hybridization (Currat et al., 2008), we believe the displacement scenario has greater support. Similar patterns of displacement have been documented in populations of warblers (Rohwer et al., 2001;Secondi et al., 2006) and marsh passerines (Walsh et al., 2016). ...
Article
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Hybridization is common in bird populations but can be challenging for management, especially if one of the two parent species is of greater conservation concern than the other. King rails (Rallus elegans) and clapper rails (R. crepitans) are two marsh bird species with similar morphologies, behaviors, and overlapping distributions. The two species are found along a salinity gradient with the king rail in freshwater marshes and the clapper in estuarine marshes. However, this separation is not absolute; they are occasionally sympatric, and there are reports of interbreeding. In Virginia, USA, both king and clapper rails are identified by the state as Species of Greater Conservation Need, although clappers are thought to be more abundant and king rails have a higher priority ranking. We used a mitochondrial DNA marker and 13 diagnostic nuclear single nucleotide polymorphisms (SNPs) to identify species, classify the degree of introgression, and explore the evolutionary history of introgression in two putative clapper rail focal populations along a salinity gradient in coastal Virginia. Genetic analyses revealed cryptic introgression with site‐specific rates of admixture. We identified a pattern of introgression where clapper rail alleles predominate in brackish marshes. These results suggest clapper rails may be displacing king rails in Virginia coastal waterways, most likely as a result of ecological selection. As introgression can result in various outcomes from outbreeding depression to local adaptation, continued monitoring of these populations would allow further exploration of hybrid fitness and inform conservation management.
... In some years, at least, the Nashville Warbler has been present in Cranberry Glades, Pocahontas County, and it has probably nested on occasion in Cranesville Swamp, Preston County. Adult birds carrying food have been seen on the Maryland side of the Cranesville Swamp (Stewart and Robbins, 1958). It has been seen in June in Blister Pine Swamp and on Gaudineer Knob, Randolph County. ...
... Within the Chesapeake Bay surveys of selected colonial waterbird colonies began in the 1940s and 1950s (Stewart and Robbins 1947, 1958, Abbott 1955. During the 1975 and 1976 breeding seasons the first systematic survey of wading bird colonies was completed in association with a broad-based survey covering the Atlantic Coast (Custer and Osborn 1977). ...
... This new focus provided a major impetus to the "nongame-bird" research field that had been quietly progressing under Robert Stewart and Chandler Robbins since the late 1940s. In spite of very limited funding, these two biologists produced a much-cited book on bird distribution throughout the Washington, D.C., and Chesapeake Bay area (Stewart and Robbins, 1958 biologist Anthony Erskine to create the North American Breeding Bird Survey (BBS), using volunteers across the U.S. and southern Canada. The first full year of the BBS was 1965, when Robbins reported that about 50,000 birds had been counted (Robbins, 1965)-a truly impressive beginning of what would later become the longest running systematic terrestrial wildlife survey in North America. ...
Article
The Patuxent Wildlife Research Center (Patuxent), first known as the Patuxent Research Refuge, has a long and rich history of participation in the Department of Interior’s (DOI) cooperative efforts to protect and conserve migratory birds in North America. This chapter describes many of the events and the people involved that constitute this important timeline for international conservation of a shared wildlife resource. The Patuxent Research Refuge, renowned worldwide, is part of the National Wildlife Refuge System of the U.S. Fish and Wildlife Service (USFWS) that has, at different times and under a variety of organizational iterations, provided the physical location of Patuxent, the Migratory Bird Population Station (MBPS), the Migratory Bird and Habitat Research Laboratory (MBHRL), and the Laurel Branch of the Office of Migratory Bird Management (MBMO, now Division of Migratory Bird Management [DMBM]). This chapter also emphasizes the interrelations between the management objectives of the USFWS and the research program at Patuxent. Following incorporation of the research program into the National Biological Survey (NBS) and subsequently into the U.S. Geological Survey (USGS), the Migratory Bird program took on new identities, while the management functions continued to evolve within the USFWS despite these changes. Nevertheless, the USFWS and other agencies such as the National Park Service (NPS) were longstanding “clients” of the research community within DOI, and many of the former linkages between management and research were maintained.
... Golden-wings have never been reported breeding here, although some migrate through. Golden-wings breed only 20 miles away, but the two species are separated by a 20-mile-wide valley where apparently neither breeds (Stewart and Robbins, 1958). This colony has been censused by local bird students since 1960. ...
... timing of arrival and breeding in Maryland is earlier for pinus. Pinus sets up territories by late February or early March, and has been observed nest building on March 4. Dominica arrives in mid-March or later and begins nest building as early as April 18 (Stewart and Robbins, 1958and personal observations). Habitat.-over ...
... Further increases and range expansion of Herring Gulls occurred during the 1950s and 1960s; the estimated number of Herring Gull breeding pairs on Long Island increased from 225 in 1951 to 5,550 in 1972 (Drury and Kadlec 1974). Although the New England Herring Gull population was apparently stabilizing during this time period (Kadlec and Drury 1968;Drury and Kadlec 1974), this species continued its range expansion southward into North Carolina (Stewart and Robbins 1958;Ames 1963;Burger 1977;Brinker et al. 2007). ...
Article
During the 20th century, gull populations in North America experienced considerable changes in abundance and geographic ranges. The objective of this study was to describe population trends of Herring Gulls (Larus argentatus) and Great Black-backed Gulls (L. marinus) in the New York Bight, USA, over a 40-year period (1974–2013). A variety of data sources using different survey methods provided estimates of the number of breeding pairs for both species. In the Long Island portion of the New York Bight, overall Herring and Great Black-backed gull nesting populations appear to have fluctuated considerably in size during this time period, and the largest numbers of breeding individuals of these two species occurred in the 1980s. In coastal New Jersey, the Herring Gull nesting population has remained relatively constant, whereas the Great Black-backed Gull nesting population has increased. Individual nesting colonies are dynamic and can vary in size considerably during even short time periods. Several factors, including sea-level changes and the availability of anthropogenic food sources (i.e., at landfills and fisheries by-catch), likely have strongly influenced individual colonies and the overall Herring and Great Blackbacked gull breeding populations in the New York Bight.
... Maryland is a mid-Atlantic state that spans 5 biotic regions (i.e., physiographic provinces) from the Appalachian Plateau (highest elevation = 1,024 m) to the Coastal Plain (lowest elevation = sea level, 0 m; Stewart and Robbins 1958; Paradiso 1969). Mixed mesophytic forest types are found at the highest elevations, with xeric oak (Quercus spp.)-hickory (Carya spp.) being the more common forest type in the Piedmont and oak-pine (Pinus spp.) in the Coastal Plain (Braun 1950). ...
Article
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Culverts have been installed beneath roadways for drainage or to contain existing streams; however, most of them have not been installed to facilitate the passage of wildlife. Prior studies of existing drainage structures used by wildlife have been narrow in scope, targeting a restricted number of culverts, time periods, or locales. Use of culverts by wildlife has been postulated to promote connectivity of fragmented populations and their habitats and to reduce roadkills. We monitored 265 culverts located throughout Maryland, USA, with game cameras in all seasons and in every physiographic province. Our objectives were to identify those species using culverts and their relative occurrence and to determine how culvert and land-use and land-cover (LULC) characteristics affect use. We documented culvert use by 57 wildlife species. We analyzed species affi liation with culvert and LULC variables for 12 species that occurred in ≥30 culverts. Different factors affected culvert use by these species. White-tailed deer (Odocoileus virginanus), in particular, used culverts that were wider, taller, and longer than unused culverts, with higher use occurring in the Piedmont physiographic province of Maryland. Our results can be used to make informed decisions on retrofitting existing culverts or designing cost-effective underpasses that provide basic wildlife needs and promote wildlife passage across roadways.
... Nowhere else in the Chesapeake Bay does there exist such an extensive region of nearly continuous estuarine marsh. Although Stewart and Robbins (1958) reported high densities of black ducks (5.3 pairs per 40.5 ha) in the expansive marshes of the Fishing Bay area, no formal studies of black ducks have ever been conducted there. A second feature of the region is the presence of the 40-km island chain consisting of Bloodsworth, South Marsh, and Smith Islands, terminating in the smaller Tangier Island in Virginia. ...
... They were also found at one site along the Patuxent River and one site on the Sassafras River. Atlas field workers found Common Moorhens scattered throughout the coastal plain (Stewart 1996) and at several locations on the western side of the Chesapeake Bay. Stewart and Robbins (1958) and Meanley (1975) considered it a common breeder along the Gunpowder River estuary, where we failed to find any. ...
Article
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The Chesapeake Bay is one of the largest estuaries in the world and the surrounding wetlands are an essential component of this ecosystem. A particularly notable feature of these wetlands is the diverse community of obligate wetland breeding birds. For example, six of the nine North American species in the family Rallidae breed in the Maryland portion of the Chesapeake Bay (American Ornithologist Union 1983). As a result of the wide diversity of emergent wetlands found within the Chesapeake Bay estuary, it is one of few regions in North America with this diverse a community of breeding marshbirds. The ecology, relative abundance, and population trends of rails and other obligate wetland breeding birds are poorly known throughout North America (Eddleman et al. 1988), including the Chesapeake Bay. During the 1950s, most of Maryland's breeding marshbirds were considered fairly common in coastal wetlands (Stewart and Robbins 1958). However, findings of the breeding bird atlas project in Maryland (Robbins and Blom 1996), conducted during the mid 1980s, suggested reduced distributions for some of these marshbirds. No reliable estimates of breeding populations for Maryland's rails and other obligate wetland breeding birds (i.e., Pied-billed Grebe, American Bittern, Least Bittern, Common Moorhen) are known. Prior to this study, no comprehensive population surveys for these species were attempted in Maryland. The atlas project (Robbins and Blom 1996) focused on breeding distributions not population numbers.
... Nowhere else in the Chesapeake Bay does there exist such an extensive region of nearly continuous estuarine marsh. Although Stewart and Robbins (1958) reported high densities of black ducks (5.3 pairs per 40.5 ha) in the expansive marshes of the Fishing Bay area, no formal studies of black ducks have ever been conducted there. A second feature of the region is the presence of the 40-km island chain consisting of Bloodsworth, South Marsh, and Smith Islands, terminating in the smaller Tangier Island in Virginia. ...
Technical Report
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Human disturbance of wintering waterfowl can be defined as any intentional or unintentional anthropogenic action that elicits a metabolic or behavioral response. Presumably any response causes an immediate increase in energy expenditure that may be offset by three generalized compensatory behaviors: increased energy intake, habituation, and dispersal. Failure to fully compensate behaviorally for increased energy expenditure may lead to reduced physiological condition. I briefly review evidence of these behavioral responses in other wintering waterfowl species and present results from a study of American black ducks (Anas rubripes) wintering at Chincoteague National Wildlife Refuge.
... Oystercatchers are large, conspicuous shorebirds that rarely go unnoticed and, therefore, comprehensive records document their arrival to new sites. The first recent nest north of Virginia was found on Assateague Island, Maryland (1939, Stewart andRobbins 1958) followed by another at Little Beach Island, New Jersey (1947, Kramer 1948), then Long Island, New York (1957, Post and Raynor 1964, and Massachusetts (1969, Finch 1970, Veit and Petersen 1993. The current breeding range extends north to Boston Harbor, Massachusetts (Veit andPetersen 1993, Nol andHumphrey 1994), but small numbers have reached Green and Stratton Islands, Maine and Cape Sable Island, Nova Scotia (1997, Myers et al. 1998, Mawhinney et al. 1999. ...
Conference Paper
Background/Question/Methods Global climate change is rapidly changing the world’s environment and is predicted to accelerate current rates of sea level rise, eventually inundating coastal areas. These changes will have an outstanding impact on organisms that rely on coastal areas and intertidal zones, especially shorebirds. One species that is susceptible to the effects of climate change on the U.S. Atlantic Coast is the American Oystercatcher (Haematopus palliatus). Future evaluations of the relative impact of climate change on shorebird populations require a comprehensive understanding of current population dynamics. We designed a stochastic population model to explore the dynamics of a local population of oystercatchers and identify the demographic parameters driving observed population trends in Massachusetts. From 2005 – 2008, we collected nesting data and conducted a mark-recapture study to parameterize this model for American Oystercatchers in Nantucket, Massachusetts. Results/Conclusions Fecundity (0.20, SE 0.03 females fledged per female) was higher than those from other Atlantic Coast populations. Furthermore, we found that egg survival was exceptionally high but chick survival was low. We used advanced mark-recapture techniques to estimate annual adult survival and breeding-site fidelity for American Oystercatchers. Our results revealed a high rate of true annual survival (0.94, SE 0.03) and a strong, but variable, degree of breeding-site fidelity (0.93, SE 0.05). Additionally, we used mark-recapture data to estimate juvenile annual survival (0.51) and subadult transition probability (0.17). Our model shows that current reproductive success is sufficient to maintain the population (λ = 0.97, 95% CI: 0.90 - 1.02), but not sufficient to predict an observed recent increase. Using reverse encounter histories, we estimated movement parameters and found approximately 7% of the population permanently emigrates while 16% of the population is likely comprised of adults immigrating into Nantucket. Demographic analyses confirmed that high immigration rates, likely related to warming climate, are responsible for the observed growth (λ = 1.08, 95% CI: 0.99 - 1.16). These modeling efforts provide a foundation for continued examination of shorebird population demographics and the evaluation of the likely influence of sea level rise (again the result of warming climate), on local populations. Furthermore, the continued monitoring of oystercatcher demographics may provide a measure of intertidal community health in the face of sea level rise. Future warming will likely lead to the continued increase of American oystercatchers, and possible decline of Black oystercatchers in the Pacific.
... are found only 20 miles away (Stewart and Robbins, 1958) this was a Blue-wing population. ...
Article
B LUE-WINGED Warblers (Vermiuora pinus) and Golden-winged War-blers (V. chrysoptera) are extensively sympatric and hybridize in areas of overlap (Berger, 1958; Short, 1962, 1963). Despite introgression, etho-logical reproductive isolating mechanisms are operating in this complex (Ficken and Ficken, 1968). Experimental analysis of auditory species dis-crimination is relevant to an understanding of the reproductive relationships in these since song is probably of some importance in species recognition. Some experiments on auditory species discrimination in Blue-winged War-blers have been conducted by Gill and Lanyon (1964). They found that if Blue-wings were given a choice between Blue-winged primary song and Golden-winv b primary song, they responded to their own species' song. We felt that weak responses to the other species song might better be detected by a "no-choice" technique. The purpose of this study was to determine if Blue-wings and Golden-wings would respond to the other species' primary song. Both species possess a primary and a secondary song. The primary song in both species is given by undisturbed males and predominates early in the nesting cycle, while secondary song is more prevalent after incubation and during and immediately following territorial encounters (Ficken and Ficken, 1966). Thus it is the primary song that is probably important in species recognition. The primary song of the Blue-wing is a short bee note followed by a buzz, and that of the Golden-win g a zee followed by several short bee notes. The primary songs of the two species, although distinctive, have some common characteristics (see spectrographs in Ficken and Ficken, 1966). The bee notes in the songs of the two species are very similar as are the pitches of the songs and the temporal relationships between notes. The secondary songs are more similar and in both species usually consist of a trill followed by a buzz (Gill and Lanyon, 1964).
... separated the Dendroica species into three breeding habitat classes: deciduous forest and scrub, coniferous forest, and mixed (use of both deciduous and coniferous habitats). I based the classifications (Fig. 1) largely on Mengel (1964), supplemented with additional information from Todd (1940), Kendeigh (1945), Brooks (1947), Griscom and Sprunt (1957), Burleigh (1958), Stewart and Robbins (1958), and Mengel (1965). Those species that Mengel (1964) designated as restricted taiga breeders I consider to be in the coniferous group, with two additions: D. pinus, which is restricted to pine forests within the deciduous forest biome, and D. magnolia, which is only rarely found away from coniferous forests or woodlands or the coniferous understory of mixed forest. ...
Article
Body size varies considerably among species of Dendroica. Larger species are nearly restricted to breeding in coniferous forests and woodlands. Among the largest warblers are species breeding in taiga and species specializing, at least in eastern North America, on spruce budworm outbreaks. On the wintering grounds large coniferous breeders may often display fea- tures of opportunistic exploitation systems: intraspecific gregariousness and labile foraging behav- ior. A detailed comparative study of Dendroica pensylvanica and D. castanea supports this general conclusion. Small body size is probably an adaptation to specialized foliage insectivory. If conifer foliage is easily exploited, if insect abundance cannot support specialization on foliage insects, or if food often occurs in abundant, easily used patches, then larger body size may evolve in response to counterselective factors. These factors might include resistance to starvation or cold stress. I propose that current coniferous-restricted species are members of species groups that evolved in association with coniferous forest, first as residents and later as migrants. Migration evolved in response to late Tertiary and Quaternary climate cooling. Perhaps generalist coniferous-breeding Dendroica were preadapted for roles as opportunists on their wintering ranges. Received 20 October 1978, accepted 8 June 1979. THE 16 species of the genus Dendroica breeding in eastern North America are similar in basic body plan. Within this group ecological divergence has been thought to be largely behavioral. Bill dimensions are strikingly similar for syntopic species (MacArthur 1958, Schoener 1965), although small variations in bill length may occasionally be important (Ficken et al. 1968). Still, given the diversity in habitat selection and microhabitat use on the breeding range, some significant interspecific variation in morphology should occur. In ad- dition, Dendroica differ in many aspects of their winter exploitation systems, and this should also select for divergent morphology. In this paper I will explore the relationship between body size, as indicated by skeletal measurements, and foraging style, habitat selection, and winter exploitation systems in eastern Dendroica. I will examine basic models of speciation and distribution changes to see whether breeding or wintering ground factors seem primarily responsible for the observed suites of characters. METHODS I measured skeletons of 178 males (7-15 per species) of 16 species of eastern Dendroica. Specimens were broadly distributed geographically to minimize the effects of geographic variation within species. I measured bony wing length (excluding the manus, which was often broken) and sternum length. These measurements will be used to index core body size. Ideally, fat-free weight should be used, but lacking these data for most of the species, these two skeletal measurements are probably an adequate substitute. Sternum length is a linear measurement of a large portion of the body cavity, and both wing bones and sternum support the mass of flight muscles that constitute a large portion of the total body weight. I compiled information on breeding habitats and winter ecology of Dendroica from a search of available literature. I also briefly summarize data I have gathered on D. pensylvanica and D. castanea in Panama during the winter from December 1976 to May 1979.
... On the East Coast the similar Least and Semipalmated Sandpipers (Ereunetes pusillus) migrate at approximately the same time (Urner and Storer 1949;Stewart and Robbins 1958). However, on the East Coast there appears to be a greater degree of habitat separation between these two species than between the Least and Western Sandpipers. ...
Article
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HE behavioral patterns of migrant shorebirds differ considerably from those of the same birds on the breeding grounds. The dynamic character of migration and the formation and maintenance of flocks contrasts with the fixed location of the nest site and the lower population densities on the breeding grounds. Population density greatly increases during migration. Species with different breeding ranges or from different habitats join together forming dense multispecific aggregations and frequenting habitats within which all foraging individuals must resort to the same horizontal plane (Recher, 1966) . Aggressive interactions between shorebirds can be observed during both the breeding and the non-breeding seasons, but may occur for very different reasons and have very different effects. During the breeding season aggres- sion is primarily associated with territoriality and courtship. During migra- tion and on the wintering grounds, aggression is primarily associated with interactions between foraging individuals. The density of foraging aggrega- tions and the restriction of individuals to the same horizontal plane creates situations in which some birds may find it difficult to maintain individual distance through avoidance movements and in which the availability of food organisms may be restricted by the presence of competing individuals. Thus it is not surprising that frequent and often prolonged aggressive interactions are a distinctive characteristic of shorebird foraging aggregations during migration. In this paper we describe the patterns of aggression observed among mi- grant shorebirds and relate these patterns to prevailing environmental condi- tions. Some consequences of aggression are also discussed. Descriptions of individual encounters, postures and movements associated with shorebird aggression will b e presented elsewhere.
... Although our current range-wide estimates of aranea Gull-billed Terns do not differ substantially from those of earlier reports, at the state level longer term declines overshadow a few shorter term increases (Fig. 3,Table 1). In Maryland the Gull-billed Tern was considered fairly common in the 1950s (Parnell et al. 1995) with a peak population size of 25-30 pairs in that decade (Stewart and Robbins 1958); during the 1980s the number of breeding pairs fluctuated from 9 in 1985 , 33 in 1986 , 1 in 1987 to 0 in 1988 (Brinker 1996) and it is now probably extirpated (fide D. Brinker). In Virginia population estimates have declined by 60% between 1977 and 2003, and in North Carolina estimates have declined by 58% between 1977 and 2001. ...
Article
The Gull-billed Tern (Gelochelidon nilotica) has until recently received little conservation and management attention within North America despite a relatively low overall population size and significant declines in parts of the breeding range. This lack of attention may stem in part from the wide distribution of the species, encompassing parts of six continents, and from its tendency to nest in relatively small, scattered and often ephemeral colonies. Populations of North American subspecies are alarmingly small. The current population of the eastern subspecies aranea in the U.S. is unlikely to exceed 3,600 pairs, with over 60% of these birds occurring in Texas. The Texas population has remained generally stable, but declines of populations in Maryland (where probably extirpated), Virginia, North Carolina, Florida, and possibly Georgia give cause for concern for this subspecies. For the western subspecies vanrossemi, as few as 250 pairs nest at only two locations in the U.S., both in California. When populations in western Mexico are considered, the entire vanrossemi population numbers only 600-800 pairs. Currently the Gull-billed Tern is listed as “endangered” or “threatened” in four states, and is considered to be of management concern in five others. The breeding range of the species has contracted and shifted slightly from its known historic range in the middle Atlantic states, but otherwise occupies its historic range in the United States and has expanded slightly to coastal southern California. Some range contraction in Mexico (e.g., in Sonora) may have occurred. In eastern Mexico, historical information is almost non-existent and knowledge of current distribution and abundance is incomplete. Main threats to populations in North America include loss of natural nesting islands through beach erosion or perturbations to estuarine functions, development or modification of upland habitats near breeding areas that may be important for foraging, and disturbances to colonies by humans and feral or human-subsidized predators. This species often nests on man-made substrates suggesting it could be responsive to management of breeding sites. Key research needs include more frequent and refined population monitoring, a better understanding of demographics, metapopulation dynamics and factors limiting populations as well as refinement of subspecies’ breeding distributions and wintering ranges.
... Bald Eagles from northeastern Canada and the United States migrate southward into the Chesapeake Bay during the late fall and early winter period (Stewart and Robbins 1958;McCollough 1986;Byrd et al . 1990). ...
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The Chesapeake Bay plays a significant role in the life cycle of Bald Eagles (Haliaeetus leucocephalus) along the entire Atlantic coast of the U.S. In addition to supporting a resident breeding population, the Chesapeake Bay is an area of convergence for post-nesting and subadult Bald Eagles from breeding populations in the southeastern and northeastern U.S. The convergence of three geographically distinct populations (northeast, southeast, and Chesapeake Bay) suggests that the Bay plays a particularly important role in the recovery of Bald Eagles in eastern North America. Since the ban on DDT and formal listing under the Endangered Species Act, the Chesapeake Bay breeding population has increased dramatically. Between the early 1970s and 2001 the population within the Bay and vicinity has grown exponentially from 60 to 646 pairs with an average doubling time of just over eight years. Reproductive rates have increased over this time period and are now similar to those documented prior to the DDT era. With the current rate of increase, the population is expected to reach saturation within the next decade. Bald Eagles continue to be vulnerable to the potential introduction of new biocides into the estuary, human disturbance within nesting and foraging areas, and the loss of habitat to urban and industrial development. The tidal fresh reaches of the estuary appear to support core breeding areas, as well as, concentration areas for migrant populations and should be priorities for long-term conservation efforts.
... Tern breeding sites vary by state and year, depending on environmental or other factors that affect the suit-ability of the habitat. Royal Terns have nested in MD since 1950 using six natural islands of which only one to two have been colonized in any one year (Fig. 1;Stewart and Robbins 1958). The most important site is Skimmer Island, which has been the only nesting site for this species in MD since 1991. ...
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Nest and chick census data gathered from 1975–2005 at all known breeding colonies of Royal (Sterna maxima) and Sandwich (S. sandivicensis) Terns in three mid-Atlantic States are reported. Nest census data were gathered sporadically in North Carolina, Virginia, and Maryland throughout this period. Royal Tern chick counts based on annual banding efforts were obtained in Maryland since 1975 and North Carolina and Virginia since 1977, while Sandwich Tern chick counts date from 1977 in North Carolina and 1980 in Virginia. Royal Tern chick counts show significant annual variation by state, and are positively correlated between North Carolina and Virginia, but negatively correlated between Maryland and both North Carolina and Virginia. Sandwich Tern nest counts showed significant annual variation in North Carolina, as did chick counts in North Carolina and Virginia. These results suggest regional, rather than local, trends in Royal Tern numbers over time. While Royal Tern numbers indicate a gradual decline in nests and chick production since the 1980s, followed by an increase in recent years, Sandwich Tern numbers have remained consistently lower than Royal Terns but stable over the entire study period. Causes for the decline in Royal Tern numbers are attributed primarily to loss of open sandy habitat from vegetational succession at breeding sites on dredged material islands and to invasive species at nesting sites, including quadraped predators. Increased habitat management and regular censusing with consistent methodology are recommended to help maintain these species at sustainable levels.
... Range prior to 2000.-We obtained records from the Breeding Bird Survey (1966-1999Patuxent Wildlife Research Center, PWRC), state Breeding Bird Atlases (Delaware, 1983(Delaware, -1987Maryland, 1983Maryland, -1987New Jersey, 1993, published reports (Harlow 1907, Stone 1937, Stewart and Robbins 1958, Moore 1989, West 1993, Clapp 1997, Mc-Cann and Battin 1999, Hess et al. 2000, Maryland miniroute data, migration cards, nest records, stomach content cards (data at PWRC), specimen records (Univ. of California, Berkeley), and amateur birders throughout the study area (see acknowledgments). We considered only records from the coastal plain between 15 May and 31 August in order to avoid taxonomic confusion between M. g. nigrescens and migrants of other Swamp Sparrow races (Mowbray 1997). ...
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We examined the distribution and abundance of the Coastal Plain Swamp Sparrow (Melospiza georgiana nigrescens) at previously occupied sites and points within potential habitat. We found Swamp Sparrows throughout their formerly documented range except in southern Chesapeake Bay. Swamp Sparrows were most common in the Mullica River region of New Jersey where we detected individuals at 78% of systematically chosen points with a mean count of 4.1 birds/point. The percentages of points with positive detections in the regions of Delaware River (39%), eastern Delaware Bay (23%), western Delaware Bay (34%), and Tuckahoe River (31%) were lower. The mean count of birds/point was between 0.4 and 0.6 in these regions. A higher resolution Poisson model of relative abundance suggested that the greatest concentrations of Swamp Sparrows occurred not only in the Mullica River area but also along northwestern Delaware Bay. Regression analysis of Swamp Sparrow counts and habitat features identified shrubs (Iva frutescens and Baccharis halimifolia) as a key habitat component. By applying density estimates generated by DISTANCE (Thomas et al. 1998) to the approximate area of potential shrub habitat along Delaware Bay, we estimated that the core population of Coastal Plain Swamp Sparrows was less than 28,000 pairs. We recommend that the Coastal Plain Swamp Sparrow be listed as a subspecies of concern by state and local governments because of its relatively small population size, restricted distribution in the mid-Atlantic region, and narrow habitat requirements.
... Subsequent breeding records throughout the early to mid-Twentieth century document a northward expansion of the breeding population and a gradual recolonization of most of the species' former range. The first breeding record in Maryland was documented in 1939 (Stewart and Robbins 1958) and records after 1940 documented continued northward expansion of breeding into New Jersey (Kramer 1948), New York (Post and Raynor 1964) and Massachusetts (Humphrey 1990). More recently, breeding pairs have been documented as far north as Maine and Nova Scotia (Mawhinney et al. 1999). ...
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The conservation status of the American Oystercatcher (Haematopus palliatus palliatus) along the Chesapeake Bay, coastal bays, and barrier island shorelines of Maryland and Virginia has been investigated in detail in recent years. The region supports approximately 700 breeding pairs with more than 80% occurring on the east coast of the Delmarva Peninsula and less than 20% occurring along the shorelines of the Chesapeake Bay. The number of breeding pairs in Maryland appears to have been stable or to have increased slightly during the past 20 years. The overall trend of the breeding population in Virginia is less clear, but recent evidence suggests that numbers on the barrier islands are increasing after more than two decades of a declining trend. The coastal bays and barrier islands typically support between 1,500 and 2,000 wintering birds with most occurring on the east coast of the Virginia portion of the Delmarva Peninsula. The shorelines of both states together play an important role in supporting core breeding and wintering populations of the American Oystercatcher in the eastern United States. Throughout the region, oystercatchers are facing threats common to all coastal waterbird and shorebird species such as predation and overwash events. The threat of habitat loss to development, however, is not as alarming as in other areas of the species’s breeding range due to a significant amount of habitat being in protective conservation ownership or being unfit for development and recreation purposes. Habitat loss attributed to sea level rise, barrier island dynamics, and the indirect effects of development, such as pollution and contaminants, may play more important roles in the stability of breeding and wintering habitat for the American Oystercatcher in Maryland and Virginia.
... In Maryland, the American Oystercatcher was considered a rare to uncommon breeding species (Stewart and Robbins 1958;Robbins and Boone 1984;Brinker 1996;Illiff et al . 1997). ...
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The Atlantic coast population of the American Oystercatcher (Haematopus palliates) has seen mixed success in its recovery from historic lows at the turn of the 20th century. During the mid-1980s, breeding numbers in Maryland were estimated at 50-75 pairs based on incidental observations and the results of the state’s first breeding bird atlas project. With growing national and regional concern for the species and a need for current information on its status in Maryland, the state’s first comprehensive survey of nesting oystercatchers was conducted during the 2003 breeding season. Both hatching success and fledging success were relatively high, with some breeding birds nesting in areas where they were not previously found in the state. Most oystercatchers nested on salt marsh islands, as opposed to the extensive barrier island found along Maryland’s coast. Although a similar number of birds nested in the Chesapeake Bay and Coastal Bays, nest success was significantly greater in the Chesapeake Bay. Landscape type proved to be the only variable that was significantly associated with statewide nest success, though it did not explain the differences in success between Chesapeake Bay and Coastal Bay birds. Several existing and potential threats require consideration in future studies and management of this species.
... Subsequent breeding records throughout the early to mid-Twentieth century document a northward expansion of the breeding population and a gradual recolonization of most of the species' former range. The first breeding record in Maryland was documented in 1939 (Stewart and Robbins 1958) and records after 1940 documented continued northward expansion of breeding into New Jersey (Kramer 1948), New York (Post and Raynor 1964) and Massachusetts (Humphrey 1990). More recently, breeding pairs have been documented as far north as Maine and Nova Scotia (Mawhinney et al. 1999). ...
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OBSERVATIONS The Saltmarsh Sharp-tailed Sparrow (Ammodramus caudacutus)has recently been listed as a species of highest conservation concern in the mid-Atlantic (Watts 1999) and Southern New England (Dettmers 2000) physiographic areas. This designation recognizes their relatively small global population, their very restricted geographic range, and the tenuous state of their breeding habitat. Distribution, abundance, and natural history information is currently needed to better refine conservation objectives. Here I describe a recent observation of breeding for the Saltmarsh Sharp-tailed Sparrow in Gloucester County Virginia and discuss this observation relative to the southern range limit throughout their breeding range. During the spring and summer of 1992and 1993I conducted a study of area-sensitivity in birds using salt marshes along the lower western shore of the Chesapeake Bay (Watts 1992,1993).The study area included the shoreline arc between Grandview Beach in Hampton to Newpoint Comfort in Mathews County. Marshes were chosen for the study based on access, location, and vegetational composition. Patches were saturated with a combination of point counts and line transects and were each surveyed 4 times between 6 May and 18July. A total of 142detections of Sharp-tailed Sparrows were made during the study primarily by flushing birds along line transects. Due to the constraints of the study, there was no opportunity to evaluate plumages enough to determine populations of origin. However, virtually all of the birds migrated out of the area in the late May to early June period. Only 14 observations were made after 10 June and nearly all of these birds left after this date. A single pair of Saltmarsh Sharp-tailed Sparrows remained throughout the entire study period. On 2 June, 1992 while walking a line transect in Four Points Marsh, a Sharp-tailed Sparrow was flushed from a nest near the ground. The bird flew less than 5 m into a patch of black needlerush (Juncusroemerianus). The nest was built in a dense mixed stand of saltmeadow hay (Spartinapatens)and saltgrass (Distichlisspicata)and was positioned against a patch of black needlerush along the edge of a tidepool. Thenest was made ofdry grasseswith afinelining and contained 4 eggs. The nest entrance was partially concealed by overhanging grass. It was not possible to closely monitor this nest but two additional surveys of this marsh were conducted and the nest was checked during those visits. On 18 June, the pair was detected in the area but the nest was empty and young were not located. On 8 July, the pair was once again detected but young could not be located. It seems likely that the nest failed during the early June period. Four Points Marsh is located in Gloucester County and is one of the best examples of a short-grass marsh in the lower Chesapeake Bay. The marsh is approximately 125 ha in area and the surface is dominated (>80%) by saltmeadow hay and saltgrass with scattered black needlerush and saltbush (Ivafrutescens). This
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Two recent nesting records for the American oystercatcher, Haematopus palliatus, establish new range limits range for this species along the Atlantic coast. In 1997, one pair of American oystercatchers was observed nesting on Green Island, Maine and another pair was observed in Clark's Harbour on Cape Sable Island, Nova Scotia. Both nests were monitored throughout the breeding season. Two of three chicks that were hatched on Green Island were believed to have fledged. However, the three chicks hatched on Cape Sable Island were believed to have been depredated by gulls nesting on the island. These are the first confirmed breeding records for the American oystercatcher at both of these locations and the nest in Nova Scotia is the first confirmed breeding record for Canada in this century.
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We conducted annual aerial surveys (1991-2011) for breeding Bald Eagles (Haliaeetus leucocephalus) within Aberdeen Proving Ground (APG), a 350-km2 military installation located along the northwestern shoreline of the upper Chesapeake Bay in Maryland. The population increased exponentially from 1 pair in 1977 to 58 pairs in 2011 with an average doubling time of 5.8 years. This rate was higher than that documented for the broader Chesapeake Bay and is comparable to the highest reported throughout the species range. Annual population increase was highly variable and exhibited no indication of any systematic decline. A total of 646 chicks were produced from 464 breeding attempts during this period. The population has exhibited tremendous forward momentum such that more than 50% of young produced over the 21-year period were produced in the last 6 years. Average success rate was high (79.8%) and reproductive rates exceeded conservation targets in nearly all years. Due to the expansion of urban development throughout the Chesapeake Bay watershed, APG plays an increasingly important role in the recovery and maintenance of the Chesapeake Bay Bald Eagle population.
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The roseate tern Sterna dougallii Montagu (Aves, Laridae) has a nearly cosmopolitan breeding distribution. The North American and European populations, the only ones which have been well-documented, have both declined drastically in the past decade, raising grave concern over the species' future. Literature search and correspondence reveal that the species currently maintains substantial breeding populations in the Indian Ocean, Caribbean, and Australasian regions. Most old reports provide no quantitative population estimates, while even many recent reports provide only vague estimates of population size. Nonetheless it has been possible to estimate regional populations in most cases to within one order of magnitude. The North American and Caribbean populations total about 10 000 pairs, while the European population is about 1500 pairs. The African population, including the Seychelles and the western Indian Ocean, may have 15 000 to 22 000 pairs. The documented world population is between 20 000 and 30 000 pairs, but the breeding populations of many areas are not yet documented. Substantial variation within and between regions in appearance and breeding biology indicates that each of the five named forms, at least, should be studied and managed separately.
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The Coastal Plain Swamp Sparrow (Melospiza georgiana nigrescens) was orig- inally described from a small number of specimens from the tidal marshes of the Nanticoke River in southeastern Maryland. Based on our quantitative analysis of a larger series of specimens, we found that Swamp Sparrows collected during the breeding season from the Chesapeake and Delaware bays (and tributaries) and near the mouth of the Hudson River are generally less rusty, have more black in the crown and nape, and have larger bills than other Swamp Sparrows. Contrary to earlier accounts, we found M. g. nigrescens to be migratory, arriving after the spring migration and departing before the fall migration of the inland subspecies through the tidal marshes. The location of the wintering grounds of M. g. nigrescens is unknown. We argue that the morphological and life history differences characterizing M. g. nigrescens reflect adaptation to tidal marshes. We base this hypothesis on the nature of the morphological differences, which are convergent with other tidal marsh breeding sparrows and other terrestrial vertebrates.
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The hypothesis that polygynous species start breeding later in the season than monogamous ones was examined using two data sets, each with both monogamous and polygynous species—the eight species of wrens which breed in the USA, and five genera (15 species) of British passerines. Comparisons were made within each of 16 states in the USA from which data were available and for each genus in Britain. The hypothesis is supported for most subsets of data, but in some cases polygynous and monogamous species start breeding at the same time (but in no case do polygynous breed earlier than monogamous species). The late breeding of the polygynous species is probably an outcome of the fact that polygynous males tend to participate less in nest activities than monogamous ones.
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For five species of morphologically very similar Corvus to occur on one continent and for two or three of these species to frequently coexist in sympatry, effective isolating mechanisms must be active to maintain species integrity. This paper describes and compares the behaviour and social organization of Corvus coronoides and C. mellori in detail; C. tasmanicus, C. orru, and C. bennetti were studied less intensively but are compared wherever possible. Few spectacular or species-specific displays were recorded. Calls are varied and a "vocabulary" for C. coronoides is given; each species has a characteristic territorial advertisement call. Both C. coronoides and C. mellovi form long-lasting pair bonds; probably the other species do so as well. Adults of C. coronoides, C. orru, and C. tasmanicus maintain territories all the year round; immatures and non-breeding adults live in nomadic flocks. C. mellori and C. bennetti occupy a breeding territory only for the minimum time (3 months) necessary to rear young; for the rest of the year they and their non-breeding conspecifics are nomadic. The number and size of C. covolzoides territories varied little over the years of the study; this and the ever-present reservoir of mature but non-breeding adults in the flocks suggest that large mosaic territories for permanently resident species may limit breeding density. The nomadism of non-breeding birds enables transient localized food-gluts to be utilized.
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The foraging behavior of Worm-eating Warblers (Helmitheros vermivorus) was studied in Maryland during the breeding season and in Jamaica, Dominican RepubUc, and Belize during the nonbreeding season. Over 75% of the foraging maneuvers recorded from May to early August in Maryland were directed towards live foliage, whereas over 75% of the maneuvers were directed towards dead curled leaves in the understory of tropical forest in the temperate zone winter. Sampling of the relative abundance of arthropods associated with dead and live foliage showed that although the ratio of total numbers in dead and live leaves was similar in the temperate and tropical sites, the overall ratio of estimated biomass was considerably greater in the tropical sites. This is because large arthropods commonly use dead curled leaves as daytime roosts in tropical forests. However, the largest temperate- zone arthropods are generally found on leaf surfaces during the day. The winter-foraging specialization on dead leaf arthropods apparently is the more demanding; the most spe- cialized search and attack behaviors are associated with feeding at dead and hve curled leaves. I revisited the Belize study sites in September, when Worm-eating Warblers were presumably arriving and found an intermediate use of dead and live leaves. Relative abun- dances of arthropods on dead and live leaves were similar to those found in the winter period at the same sites. This suggests a period of transition which is consistent with the trial and error learning hypothesis for the development of seasonal foraging specializations in this species.
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HE New World genus Catoptrophorus has been placed between Hetero- scelus and Totanus in the American Ornithologists' Union Check-list of North American Birds (1957). Th ere is but a single species, divided into two subspecies, semipalmatus and inornatus. The current edition of the Check-list does not provide common names below the species level, but it is convenient, and should confuse no one, to continue to use the terms "Eastern Willet" for C. s. semipalmatus and "Western Willet" for C. s. inornatus, although the terms "coastal" and "inland" would be more appropriate. Some confusion as to the status of the two forms on the western Gulf coast has existed in the past. Ridgway (1919) considered that the breeding form on the coast of Texas was inornatus, although he gave one breeding record for semipalmatus from Texas. Griscom and Crosby (1925:440, 531), aware of this confusion, collected breeding specimens from the vicinity of Brownsville, Texas, which Jonathan Dwight examined and identified as semipalmatus. However, they considered that the breeding birds from northeast Texas were probably of the western form. Subsequently, Bent (1929) concluded that all the coastal breeders were semipalmatus and that inornatus breeds only inland in the western states and the Canadian provinces. This view has been con- curred in by others, and the ranges are so indicated in the 4th edition (1931) and the 5th edition (1957) of the A.O.U. Check-list. Ridgway's (1919) mea- surements and descriptions need to be revised to accord with this latter de- termination of the distribution of the two subspecies. The ranges of these two subspecies as quoted from the current Check-list are: C. S. semipalmatus-"Breeds in southwestern Nova Scotia (locally) and from southern New Jersey and Delaware south along the Atlantic coast to Florida; from extreme southern Texas (possibly Tamaulipas) eastward along the coast of Louisiana, the islands off southern Mississippi and Alabama, to the west coast of Florida; also locally in the West Indies (the Bahamas, Grand Cayman, Beata Island, St. Croix, Antigua). Winters locally along the Gulf of Mexico coast (Tamaulipas, Texas, Louisiana, Florida), on the south Atlantic coast from Virginia to Florida, and in the West Indies (Bahamas, Greater Antilles) ; south to Central America (rarely on the Pacific side), Venezuela (Margarita Island), British Guiana, and northern Brasil (Par&). Casual north to Newfoundland and Prince Edward Island." C. s. inornatus-"Breeds locally from eastern Oregon, Idaho, central Alberta, southern Saskatchewan, and southern Manitoba south to northeastern California, western Nevada (Douglas County), central Utah, northern Colorado, western and northern Nebraska (rarely), and eastern South Dakota; formerly in western and southeastern Minnesota and Iowa. Recorded in summer south along the Pacific coast of Mexico to Panama and Ecuador. Winters locally from northern California (Humboldt Bay) south to the Galapagos
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Invasions by non-indigenous species (NIS) are recognized as important stressors of many communities throughout the world. Here, we evaluated available data on the role of NIS in marine and estuarine communities and their interactions with other anthropogenic stressors, using an intensive analysis of the Chesapeake Bay region as a case study. First, we reviewed the reported ecological impacts of 196 species that occur in tidal waters of the bay, including species that are known invaders as well as some that are cryptogenic (i.e., of uncertain origin). Second, we compared the impacts reported in and out of the bay region for the same 54 species of plants and fish from this group that regularly occur in the region's tidal waters. Third, we assessed the evidence for interaction in the distribution or performance of these 54 plant and fish species within the bay and other stressors. Of the 196 known and possible NIS, 39 (20%) were thought to have some significant impact on a resident population, community, habitat, or process within the bay region. However, quantitative data on impacts were found for only 12 of the 39, representing 31% of this group and 6% of all 196 species surveyed. The patterns of reported impacts in the bay for plants and fish were nearly identical: 29% were reported to have significant impacts, but quantitative impact data existed for only 7% (4/54) of these species. In contrast, 74% of the same species were reported to have significant impacts outside of the bay, and some quantitative impact data were found for 44% (24/54) of them. Although it appears that 20% of the plant and fish species in our analysis may have significant impacts in the bay region based upon impacts measured elsewhere, we suggest that studies outside the region cannot reliably predict such impacts. We surmise that quantitative impact measures for individual bays or estuaries generally exist for ,5% of the NIS present, and many of these measures are not particularly informative. Despite the increasing knowledge of marine invasions at many sites, it is evident that we understand little about the full extent and variety of the impacts they create—singly and cumulatively. Given the multiple anthropogenic stressors that overlap with NIS in estuaries, we predict NIS-stressor interactions play an important role in the pattern and impact of invasions.
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The biota of Plummers Island, Maryland, the research home of the Washington Biologists' Field Club, has been the subject of countless biological investigations over the last 100 years. While the flora and vertebrate fauna are fairly well known, the invertebrate fauna remains poorly documented with the exception of several families of insects. This paper presents a brief description of the site, notes on land-use over the last 100 years, and comments on collecting and research activities focused on invertebrates. It also serves as an introduction for the contributions that constitute this volume—a collection of papers on various aspects of the invertebrate fauna.
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Among the unusual breeding habits of the non‐parasitic Yellow‐billed and Black‐billed Cuckoos of North America are great variability in clutch size and rate of laying, initiation of incubation long before the clutch is complete, occasional laying in nests of other species, annual irregularity in the timing of the breeding season, and semi‐nomadic post‐migratory movements into breeding areas where food is abundant. These facts, in addition to their peculiar diet and the very large size of their eggs, suggest that cuckoos have extraordinary problems in obtaining adequate energy for reproduction. At Bloomington, Indiana (U.S.A.), during a 15‐year period, anomalies in the reproductive activities of cuckoos were concentrated into two years in which food was abundant. This was particularly true of one of these years, when there was a vast emergence of periodical cicadas: the Yellow‐billed Cuckoo advanced its normal schedule and bred during peak cicada abundance, laid unusually large clutches, and parasitized Black‐billed Cuckoo nests. Some females may have resumed laying in nests in which, having already deposited clutches of normal size, they had been incubating for long periods; the alternative possibility is that there was intraspecific brood parasitism. The erratic egg‐laying behaviour of these cuckoos is attributed to the evolution of mechanisms permitting very quick exploitation of a favourable feeding situation. It is suggested that reproductive behaviour has become so responsive to an abundance of food that normal ordering and integration of the stages of breeding have been lost in some females. Such a loss could be responsible for the laying of eggs in alien nests, and it may have been the antecedent of obligate brood parasitism in parasitic cuckoo species.
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Great black-backed gulls,Larus marinus, were observed to attack and kill lesser scaup, ruddy duck, and the horned grebe in the Chesapeake Bay region during late winter and early spring. Waterfowl predation by this gull has been reported in more northern waters. Such behavior is of little importance in the total mortaility of ducks. Records indicate that, while sporadic in occurrence, this gull is apparently more common in Chesapeake Bay during very cold winters than has previously been reported, and is increasing in numbers in this region.
Article
Results of a 1962 mid-winter census of the American bald eagle,Haliaeetus leucocephalus, present in the greater Chesapeake Bay region are reported. Ground observations supplemented by some aerial coverage located 200 eagles of which 24 per cent were immature birds. Previous attempts to estimate eagle abundance through nest surveys in the region are reviewed. Though this census offers the most complete estimate of eagle abundance in this region at any one time, similar counts coupled with nesting success studies should be conducted on an annual basis for several years to fully understand the true status of this species in this area.
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