Although there is a clear link between early arrival on the breeding grounds and fitness in migratory birds, how winter and staging site use influence the timing of migration events prior to arrival at breeding areas is not well established. Therefore, there is a need to characterize the migration phenology of long-distance migratory birds. This study investigated the northbound migration timing of Sanderlings (Calidris alba) along the Central and Mississippi Flyways (i.e., the ‘Midcontinental Flyway’). Between 2015 and 2017, coded nanotags were attached to 120 Sanderlings in three staging areas in the USA portion of the Gulf of Mexico: North Padre and Bolivar Flats, Texas and sites in Louisiana. Individuals were then tracked northward using the Motus Wildlife Tracking System. Sanderling detections in more northern latitudes on northward migration were primarily in Saskatchewan (94%; n = 33), with only two individuals detected along the Atlantic coast. Sanderlings trapped in North Padre arrived later in Saskatchewan than individuals trapped in Bolivar Flats and Louisiana. Additionally, there was a negative association between Saskatchewan arrival timing and staging duration, such that later-arriving individuals from North Padre had significantly shorter staging durations and consequently departed from Saskatchewan at the same time as individuals originating from Bolivar Flats and Louisiana. These results provide new insight into the migration schedule of a declining long-distance migratory shorebird species and show how departure and arrival timing are linked across disparate staging sites.

We assessed δ¹³C and δ¹⁵N profiles and endoparasite community composition in Great Egrets (Ardea alba), Great Blue Herons (A. herodias), and White Ibis (Eudocimus albus) from four wildlife rescue centers (two mainland, two on islands in the Florida Keys) in south Florida, USA to elucidate feeding ecology. We detected among-species differences for δ¹⁵N but not δ¹³C and noted decreased δ¹³C enrichment in Great Egrets and Great Blue Herons (but not White Ibis) from these centers. Parasite component community and infracommunity species richness were higher in Great Egrets and Great Blue Herons relative to White Ibis, and higher in birds of the same species from mainland centers. Multivariate analysis of parasite infracommunity structure detected co-occurring clusters of parasite taxa characteristic of Great Egrets and Great Blue Herons on the one part, and of White Ibis on the other; mainland Great Egrets and Great Blue Herons had similar parasite communities and clustered separately from conspecifics from the islands. We detected a significant (negative) correlation of infracommunity species richness with δ¹³C but not δ¹⁵N. Lastly, parasite infracommunity Bray-Curtis similarity correlated significantly with stable isotope Euclidean distances. We conclude that the two approaches converge towards similar outcomes, providing complementary and consilient information on host feeding ecology.

The feeding habitats of Great (Ardea alba) and Snowy (Egretta thula) egrets at the Great Marsh in Northeastern Massachusetts, USA, were characterized through field observations over two years during the breeding seasons of 2012 and 2013. Both species were from a large breeding colony making a daily commute to the Great Marsh for foraging. Habitats at the Great Marsh were delineated as marsh pools, the vegetated marsh, impoundments, open water, tidal flats, and tidal creeks and ditches. Observations (45 counts in 2012 and 48 in 2013) consisted of recording the number of birds, behavior (feeding or not), habitat, and the time of observation and relating these observations to the tidal cycle. The preferred feeding habitats of Snowy Egrets were in marsh pools and along the edges of large impoundments. The preferred feeding habitats of Great Egrets were on the marsh platform, particularly at high tides, and marsh pools. An analysis of physical characteristics with locations of feeding sites revealed no consistent patterns. Certain sites would occasionally support large numbers of feeding Great and Snowy egrets one day only to be ignored the next day at the same tide. The results suggest that Great and Snowy egrets are opportunistic in their selection of feeding sites at the Great Marsh. A future of wetter marshes might provide more feeding opportunities for Great and Snowy egrets, at least in the short-term.

Unmanned aerial vehicles (UAVs) can improve detection and count accuracy of avian species and provide an inexpensive alternative to surveying waterbirds compared to ground counts and other aerial methods. To validate this method for surveying colonial waterbirds in logistically challenging areas, we compared counts from images collected with a fixed-wing UAV to ground counts using a marked-subsample method or direct counts at three study sites: 1) in an open field using decoys that represented three colonial waterbird species; 2) constructed platforms in a swamp with colonial nesting Great Egrets (Ardea alba); and 3) an island with a large nesting colony of Brown Pelicans (Pelecanus occidentalis). Estimates or direct counts from UAV images were not significantly different from a known number of decoys or ground counts for Great Egrets but were almost twice as high compared to ground counts for juvenile Brown Pelicans. UAV flights did not cause either Great Egrets or Brown Pelicans to flush from nesting areas while ground surveys flushed the majority of adult Brown Pelicans from the survey area. UAV surveys captured images of eggs in nests that could not be observed by ground surveyors. Our results indicate that UAVs can provide a cost-effective and efficient method of surveying waterbirds with similar or improved results and little disturbance of colonies compared to ground counts.

Understanding space use by endangered species is important for conserving their populations, especially in locations that have a great degree of human activity. Transmitters that provide high spatial resolution have only recently become available for small-bodied animals and show promise for providing new information on habitat use. However, as with any new technology it is important to assess adverse effects on study species. We tested the efficacy of using 1.1-g miniaturized GPS units to document the breeding and post-breeding movements of adult Piping Plovers (Charadrius melodus) from the federally threatened Atlantic Coast population. We also assessed the potential impact of these miniaturized GPS units on nest survival, chick survival, and apparent adult survival rates. We found that Piping Plover movements to and from nesting areas were related to tidal stage, we documented Piping Plovers to be using previously undocumented foraging areas during the breeding season, and we obtained fine resolution habitat use data for two birds on their wintering areas in the Bahamas. The attachment of a GPS tag had no effect on apparent weekly survival of adults, and we found no differences in daily nest survival and chick survival rates between pairs with GPS tags and controls. GPS tags did not appear to adversely impact Piping Plovers during the breeding season, yet lower return rates of GPS tagged birds than controls might suggest potential negative effects on survival. While GPS tags offer a valuable tool to evaluate habitat use of this threatened species on the breeding grounds, long-term tracking needs further investigation.

The Clapper Rail (Rallus crepitans) is an avian marsh specialist that depends exclusively on coastal wetlands for all aspects of its life cycle, and is valued for its role as an indicator of ecosystem health. This study used radio telemetry in the Ashepoo-Combahee-Edisto Basin in South Carolina, USA, to assess Clapper Rail habitat selection in response to local and landscape variables and to investigate possible demographic consequences of differences in habitat selection. Compared to simulated home ranges, observed Clapper Rail home ranges during the breeding season contained greater amounts of potential forage area and shorter distances to potential forage locations at both local and landscape scales. Mean (± SE) Clapper Rail home range size was 1.06 ha ± 0.19. There were no significant differences between males (1.05 ha ± 0.26) and females (1.08 ha ± 0.25) in home range size. Home range selection based on optimization of potential forage resources may have demographic consequences for Clapper Rails; however, this hypothesis was only weakly supported. Clapper Rails foraging near exposed edges may increase mortality risk through predation, but this behavior may be negligible to survival provided that sufficient nearby cover exists. Resource abundance near cover is likely a major driver of habitat selection and is influencing Clapper Rail habitat selection at multiple scales, which may have consequences for adult survival.

The American Oystercatcher (Haematopus palliatus palliatus) is an important breeding species along the Texas Gulf Coast, particularly between Galveston Bay and Corpus Christi, Texas, USA. American Oystercatchers are considered a species of greatest conservation need and are on the priority list for conservation by the National Fish and Wildlife Foundation. American Oystercatchers feed mainly on oysters (Ostreidae) and other bivalves, which are known to accumulate significant amounts of pollutants. We determined accumulation and potential effects of environmental contaminants, particularly organochlorine (OC) pesticides and polychlorinated biphenyls (PCBs) in blood of American Oystercatchers nesting along the Texas Gulf Coast, USA during 2012 and 2013. Plasma concentrations of OCs and PCBs were low. The most commonly detected OC pesticides were HCB, HCH, α chlordane, endosulfan, methoxychlor, p,p'-DDD, and p,p'-DDE. Total p,p'-DDE concentrations ranged from 2-10 ng/mL ww and total PCB concentrations ranged from 2-54 ng/mL ww. Mean p,p'-DDE concentrations were similar among regions; however, total PCBs were significantly greater (P = 0.0056) in blood from adult birds from West Galveston Bay, Texas, USA in 2013 than in blood from young collected in 2012, mostly also from West Galveston Bay. Overall, concentrations of OC pesticides in plasma were low; however, some PCB concentrations were above the NOAEC levels that have been associated with normal reproduction in other bird species.

Among some Arctic-nesting geese, mass at fledging impacts first-year survival and recruitment into the breeding population, but this might not be true for temperate-nesting geese. For 25 years, we examined what variables impacted survival and recruitment of 731 Canada Geese (Branta canadensis) fledglings raised in Connecticut, USA by tracking individually marked birds throughout their lives. At fledging, the number of females (391) were similar to males (340), but by the end of the first year of life, females (247) outnumbered males (187). This can be explained due to the apparent survival rates for juvenile females (0.63) being higher than for males (0.55). Dispersal rate from natal areas were similar for males and females during the first year of life and cannot account for why females outnumbered males after one year of life. Apparent survival rates of female fledglings to the end of the second year was 0.48. For the 247 females still alive at the end of their first year of life, 190 were still alive at the end of their second year of life, yielding a 0.77 apparent survival rates during their second year of life. Sex was the only variable that explained the survival of fledglings until the end of their first year of life. The probability of females surviving the second year of life was not influenced by hatching date, fledging age, fledging mass, or family type. Heavier females at fledging were more likely to be recruited into the breeding population than lighter ones. Our results indicate that while an inability to acquire sufficient mass as a gosling does not affect survival, it impacts the ability to be recruited.

Sea level rise from anthropogenic climate change threatens waterbird species worldwide. In New Jersey, USA, one such waterbird, the Black Skimmer (Rynchops niger), uses both salt marsh islands and beaches for nesting colony sites. Both habitats vary in flood risk, with salt marsh islands typically being more vulnerable especially in the face of sea level rise. Given that sea level has increased in the mid-Atlantic region over the past four decades, we hypothesized that Black Skimmers have shifted their colonies from salt marshes to beaches, and that this change has led to an increase in coexistence with Least Terns (Sternula antillarum). We analyzed 44 years of seabird population census data from New Jersey and found that the probability that a Black Skimmer colony was located on a salt marsh island, as opposed to a beach, significantly declined over the survey period. Additionally, the probability of coexistence with Least Terns significantly increased. Such climate change driven population shifts of endangered species may have significant consequences for their conservation in human modified systems where habitat is already limiting.

West Nile virus activity was evaluated within an island waterbird nesting colony with > 1,250 birds at Riverside Reservoir, Weld County, Colorado, USA. To avoid disturbance of nesting birds, blood-engorged mosquitoes (Culex tarsalis) were used to sample blood indirectly from birds rather than capturing, sampling, and releasing live birds. Local virus activity was confirmed by West Nile virus-positive feather samples from 26% of 46 carcasses collected during monthly visits to the colony from June to September 2009, including American White Pelican (Pelecanus erythrorhynchos; n = 7), California Gull (Larus californicus; n = 1), Snowy Egret (Egretta thula; n = 2), and Cattle Egret (Bubulcus ibis; n = 2). Of 22 blood-engorged mosquitoes collected and the blood meal host identified to species, one West Nile virus infection was detected (putatively from a Snowy Egret), and West Nile virus-specific antibodies were detected in eight samples: Snowy Egret (n = 5), Great Blue Heron (Ardea herodias; n = 2), and American White Pelican (n = 1). The engorgement rate of female Culex tarsalis at the nesting colony was 34%, sixfold higher than that at a nearby mainland site of 5.3%. The utilization of mosquitoes for sampling blood from wild animals may have broader application, and potentially reduce human disturbance of sensitive nesting bird species.

The diet composition and prey length of the Great Crested Grebe (Podiceps cristatus) and the Red-throated Diver (Gavia stellata) co-occurring in late autumn in two reservoirs was studied. Their diet was analyzed based on carcasses from incidental mortality of individuals in fishery gill net surveys in two different freshwater reservoirs (one deep, one shallow) in southern Poland during autumn migration (October - December). Five fish species were identified in the diet of the Great Crested Grebe and nine fish species were identified in the diet of the Red-throated Diver. The proportion of a particular fish species in diet was different between the studied bird species. The ruffe (Gymnocephalus cernua) was the most common prey in the diet of the Great Crested Grebe at both reservoirs. The diet of Red-throated Diver was dominated by roach (Rutilus rutilus) at the deep reservoir and the zander (Sander lucioperca) at the shallow one. The Red-throated Diver consumed larger fish than the Great Crested Grebe at both reservoirs.

Accounts of same-sex nesting behaviors have been observed in several wild and captive bird species, but the evolutionary adaptation of this behavior remains unclear. There have been reports of male-male and female-female territorial pairs of Whooping Cranes (Grus americana) in two reintroduced populations. However, this is the first documentation of nesting behavior of a same-sex pair of Whooping Cranes. The incubation rhythm and nesting behaviors of a female-female Whooping Crane pair nesting at McMillan Marsh Wildlife Area in Marathon County, Wisconsin, USA, were documented using a nest camera. The female-female pair displayed comparable nest constancy (99.7%) and incubation behaviors to male-female Whooping Crane pairs in the same population. Both females of the pair incubated the nest; however, the older female incubated for longer periods of time than the younger female (235.8 ± 20.7 min and 168.3 ± 17.2 min, respectively). The pair exchanged incubation duties 5.7 ± 0.2 and 1.1 ± 0.2 times daily during daylight hours and nighttime hours, respectively. The two females incubated the nest for at least 28 days, but fate of the eggs was not determined. Ultimately, the cause of this pairing remains unknown. This behavior could have implications for the breeding success of this small, reintroduced population of Whooping Cranes.

There is a gap in knowledge of dispersal and migration behavior for many South American waterfowl species. This study presents data describing the movements of three individual Yellow-billed Pintails (Anas georgica) tracked with GPS-satellite telemetry that migrated via a trans-Andean Mountains crossing from Chile to Argentina. The frequency of this dispersal suggests that it is not an unusual behavior for the species, showing a possible facultative migratory trait, using different flight paths for the Andean crossing. Finally, there is evidence suggesting that there may be a migratory pattern behind the movements of southern South American populations after breeding season.

This note describes interactions between four bird species during a predation attempt by Yellow-footed Gull (Larus livens) on an Eared Grebe (Podiceps nigricollis).The interactions among species were documented on video in a mangrove (Rhizophora mangle and Avicennia germinans) area of the Ensenada La Paz (a RAMSAR site) during winter in the southwest Gulf of California, Mexico on 2 February 2019. This is the first report that has documented an effective killing attempt in the Baja California Peninsula and the second in northwestern Mexico of Yellow-footed Gull predation on Eared Grebe. Additionally, kleptoparasitism attempts against the Yellow-footed Gull by a Great Blue Heron (Ardea herodias) and Turkey Vulture (Cathartes aura) are described and suggest that those species may include prey stolen from gulls (family Laridae) more regularly than presently known based on this opportune observation.

Miniature transmitters now permit ornithologists to track the annual cycle of smaller (< 150 g) marine birds. To assess annual movements of Common Terns (Sterna hirundo) and endangered Roseate Terns (S. dougallii), 2.5 g satellite transmitters were attached with backpack harnesses. Using the same capture techniques and investigator to fit harnesses, five Common Terns were tagged in Maine in 2017, and 10 Roseate Terns in New York, USA in 2018. Common Terns were tracked from 102 – 652 days to destinations as far as Brazil with no documented adverse impacts. Three of five Common Terns returned to Maine, USA one year after tagging, and non-functioning tags were recovered from two Common Terns in 2018 and 2019. In contrast, Roseate Terns were tracked for only 1 – 72 days before transmissions ceased, with only two birds tracked for > 7 days. We detected three Roseate Terns with their bill stuck in the harness material, with one documented mortality. Common Terns tolerated the tags and provided useful data on annual movements but were not a suitable surrogate for predicting the effects of backpack mounted transmitters on Roseate Terns. Researchers considering tracking Roseate Terns should avoid using backpack harnesses.

Despite a wide distribution over much of the New World, the behavior of the Least Grebe (Tachybaptus dominicus) is still poorly known, and most ecological studies have been performed on Northern Hemisphere subspecies. This note reports two observations during breeding in the South American subspecies T. d. brachyrhynchus. Deliberate egg-covering to hide an active nest from an approaching threat was observed, coupled with elusive “hiding” behavior during an opportunistic breeding attempt in a novel habitat (xeric Chaco). Photographic documentation of egg destruction by a domestic Muscovy Duck (Cairina moschata) at a Least Grebe nest is also reported.