Entire Breeding Range Research Articles

A nomenclatural history of Audubon's Shearwater with designation of a neotype forPuffinus lherminieriLesson, 1839 (Aves: Procellariidae)

The nomenclatural history of the small Antillean species that now goes by the name Audubon's Shearwater Puffinus lherminieri is briefly summarized. The type material of Puffinus lherminieri Lesson, 1839, supposed to be in a museum in Rochefort, France, could not be located and is presumed lost. The stated type locality “ad ripas Antillarum” is so general as to encompass almost the entire breeding range of the species, which is widely distributed in the Antillean region and has been regarded as showing variation meriting subspecific designation. Although the type locality was apparently legitimately restricted to Guadeloupe in 1948 or earlier, it was elsewhere erroneously restricted to “Straits of Florida” from 1931 to 1998 and up to the present. To resolve these numerous conflicts and uncertainties, a neotype collected in Saint Barthélemy, once administratively part of Guadeloupe, is here designated.

Population Structure and Dispersal Patterns within and between Atlantic and Mediterranean Populations of a Large-Range Pelagic Seabird

Dispersal is critically linked to the demographic and evolutionary trajectories of populations, but in most seabird species it may be difficult to estimate. Using molecular tools, we explored population structure and the spatial dispersal pattern of a highly pelagic but philopatric seabird, the Cory's shearwater Calonectris diomedea. Microsatellite fragments were analysed from samples collected across almost the entire breeding range of the species. To help disentangle the taxonomic status of the two subspecies described, the Atlantic form C. d. borealis and the Mediterranean form C. d. diomedea, we analysed genetic divergence between subspecies and quantified both historical and recent migration rates between the Mediterranean and Atlantic basins. We also searched for evidence of isolation by distance (IBD) and addressed spatial patterns of gene flow. We found a low genetic structure in the Mediterranean basin. Conversely, strong genetic differentiation appeared in the Atlantic basin. Even if the species was mostly philopatric (97%), results suggest recent dispersal between basins, especially from the Atlantic to the Mediterranean (aprox. 10% of migrants/generation across the last two generations). Long-term gene flow analyses also suggested an historical exchange between basins (about 70 breeders/generation). Spatial analysis of genetic variation indicates that distance is not the main factor in shaping genetic structure in this species. Given our results we recommend gathering more data before concluded whether these taxa should be treated as two species or subspecies.

Current status of the threatened Olrog’s GullLarus atlanticus: global population, breeding distribution and threats

SummaryOlrog’s GullLarus atlanticusbreeds only in Argentina and is currently categorized as “Vulnerable”. Knowledge of the location of colonies and an updated understanding of human activities that may impact their breeding populations are crucial to the development of adequate conservation and management actions. In this paper we update the breeding distribution and abundance of Olrog’s Gull, using information from three aerial surveys (2004, 2007 and 2009) in its main breeding area, Buenos Aires Province, complemented by additional nest counts in southern Chubut Province, covering its entire breeding range. We also provide an updated and more detailed account of threats faced by Olrog’s Gulls at their nesting grounds, and summarise progress made towards their protection. The number of breeding sites was 7–12 per year, with locations differing among years. Five previously unrecorded breeding locations were identified. Colony size ranged from 5 to 3,540 breeding pairs, with the total breeding population 4,860–7,790 pairs, 98% of which nest in southern Buenos Aires Province. The main threats faced by breeding Olrog’s Gulls include coastal development, pollution, sport fishing and unregulated tourism and recreational activities. Recent strengthening of the protected area system in Argentina has resulted in all known breeding sites, with the exception of Isla Brightman, falling within protected areas. We need comprehensive, simultaneous surveys to track global population trends. Despite enhanced protection of Olrog’s Gull breeding populations, efforts are still needed to ensure that guidelines for their protection are included in management plans and that these are implemented effectively.

Minimal Genetic Structure in the Cerulean Warbler Despite Evidence for Ecological Differentiation among Populations

Abstract. The Cerulean Warbler (Setophaga cerulea) is one of the most rapidly declining warblers in North America. Our previous genetic work suggested that this migratory songbird has no significant population genetic structure in the northern and western parts of its breeding range, and for conservation purposes we assigned all sampled populations to a single genetic management unit. Here, we expand this work to include the entire breeding range of the Cerulean Warbler, given recent evidence for morphological and ecological differentiation between the northern and southern sections of that range. We assayed variation in four microsatellite loci and an 841-base-pair fragment of the mitochondrial control region, finding support for low but significant population-genetic structure in the mitochondrial marker. Estimates of population-genetic structure for pairs of sampling locations did not detect a clear geographic pattern of differentiation, and a hierarchical AMOVA did not reveal significant structure bet...

Population connectivity buffers genetic diversity loss in a seabird

BackgroundAncient DNA has revolutionized conservation genetic studies as it allows monitoring of the genetic variability of species through time and predicting the impact of ecosystems’ threats on future population dynamics and viability. Meanwhile, the consequences of anthropogenic activities and climate change to island faunas, particularly seabirds, remain largely unknown. In this study, we examined temporal changes in the genetic diversity of a threatened seabird, the Cory’s shearwater (Calonectris borealis).FindingsWe analysed the mitochondrial DNA control region of ancient bone samples from the late-Holocene retrieved from the Canary archipelago (NE Atlantic) together with modern DNA sequences representative of the entire breeding range of the species. Our results show high levels of ancient genetic diversity in the Canaries comparable to that of the extant population. The temporal haplotype network further revealed rare but recurrent long-distance dispersal between ocean basins. The Bayesian demographic analyses reveal both regional and local population size expansion events, and this is in spite of the demographic decline experienced by the species over the last millennia.ConclusionsOur findings suggest that population connectivity of the species has acted as a buffer of genetic losses and illustrate the use of ancient DNA to uncover such cryptic genetic events.

Large‐scale geographic variation in iridescent structural ornaments of a long‐distance migratory bird

Iridescent colours produced during moult likely play an important role in pair formation in birds. We sought to quantify geographic variation in such colouration in a duck species, Eurasian teal Anas crecca, in winter (when mating occurs) to evaluate whether this variation reflects birds’ breeding origins or differential individual migration strategies in both males and females. We combined information on feather production region and individual attributes (body size, sex and age) of Eurasian teal from 82 wintering sites in France. Feather production region (moult site or natal origin) was inferred using feather deuterium values (δDf). We performed spectral measurements to evaluate speculum colour and brightness contrasts for 1052 teal collected over four years. Colouration differed strongly among wintering regions, with birds wintering in eastern France exhibiting higher colour contrast than those wintering in the west. Body size and colouration were positively related. There were no differences in cohort‐specific δDf values between separate wintering regions in France, indicating that within a winter quarter teal originated from areas across the entire breeding range. Overall, patterns of spatial variation in feather colouration were related most closely to body size which was consistent with predictions of a differential migration hypothesis, with larger and more colour‐contrasting birds wintering closer to their breeding grounds. Because moult speed is also known to affect colour production, early breeders or individuals that skipped reproduction may have invested more or earlier in their feather quality to gain potential advantages in monopolizing future mates.

Small Population Size of the Pribilof Rock Sandpiper Confirmed through Distance-Sampling Surveys in Alaska

Abstract. The Rock Sandpiper (Calidris ptilocnemis) is endemic to the Bering Sea region and unique among shorebirds in the North Pacific for wintering at high latitudes. The nominate subspecies, the Pribilof Rock Sandpiper (C. p. ptilocnemis), breeds on four isolated islands in the Bering Sea and appears to spend the winter primarily in Cook Inlet, Alaska. We used a stratified systematic sampling design and line-transect method to survey the entire breeding range of this population during springs 2001–2003. Densities were up to four times higher on the uninhabited and more northerly St. Matthew and Hall islands than on St. Paul and St. George islands, which both have small human settlements and introduced reindeer herds. Differences in density, however, appeared to be more related to differences in vegetation than to anthropogenic factors, raising some concern for prospective effects of climate change. We estimated the total population at 19 832 birds (95% CI 17 853–21 930), ranking it among the smallest ...

Season length influences breeding range dynamics of trumpeter swans Cygnus buccinator

AbstractThe breeding range of large‐bodied waterfowl nesting in the northern boreal forest is likely influenced by breeding season length. This may be particularly true for the largest species of North American waterfowl, the trumpeter swan Cygnus buccinator, due to the extended time period necessary to raise young to fledging. This species recently recovered from near‐extinction in the early 1900s to reoccupy historic breeding areas throughout the boreal forest in Alaska, although recolonization patterns may have been influenced by variation in season length over the same time period. This may have resulted in range expansion into areas that were historically unavailable due to an ice‐free period insufficient for successful reproduction. We used hierarchical occupancy models to analyze trumpeter swan survey data collected over the entire breeding range in Alaska during 1968‐2005. We fit models containing combinations of recolonization parameters, trend and latitude, and season length to these data to determine whether these variables explained the variation in occupancy across our survey area. Support for season length parameters would provide evidence that the recolonization process was partially related to the length of the breeding season. We expected that occupancy probability would increase range‐wide due to overall population growth, while occupancy would be greatest at mid‐latitudes, near the center of the species range. Because this population was recovering, we also expected that expansion would proceed outward from the range center. Our results indicated that habitat occupancy was positively related to season length, partially explaining the recently observed northward range expansion. Our results suggest that increases in annual temperatures due to climate warming would likely be associated with further range expansion in trumpeter swans and may have implications for other wetland obligates. Changes in species distributions will likely increase competition for breeding areas with potential negative effects on species not limited by season length. This may already be occurring in Alaska where the breeding distribution of trumpeter swans has begun to overlap with that of tundra swans Cygnus columbianus.

Hybrid speciation in sparrows I: phenotypic intermediacy, genetic admixture and barriers to gene flow

Homoploid hybrid speciation is thought to require unusual circumstances to yield reproductive isolation from the parental species, and few examples are known from nature. Here, we present genetic evidence for this mode of speciation in birds. Using Bayesian assignment analyses of 751 individuals genotyped for 14 unlinked, nuclear microsatellite loci, we show that the phenotypically intermediate Italian sparrow (Passer italiae) does not form a cluster of its own, but instead exhibits clear admixture (over its entire breeding range) between its putative parental species, the house sparrow (P.domesticus) and the Spanish sparrow (P.hispaniolensis). Further, the Italian sparrow possesses mitochondrial (mt) DNA haplotypes identical to both putative parental species (although mostly of house sparrow type), indicating a recent hybrid origin. Today, the Italian sparrow has a largely allopatric distribution on the Italian peninsula and some Mediterranean islands separated from its suggested parental species by the Alps and the Mediterranean Sea, but co-occurs with the Spanish sparrow on the Gargano peninsula in southeast Italy. No evidence of interbreeding was found in this sympatric population. However, the Italian sparrow hybridizes with the house sparrow in a sparsely populated contact zone in the Alps. Yet, the contact zone is characterized by steep clines in species-specific male plumage traits, suggesting that partial reproductive isolation may also have developed between these two taxa. Thus, geographic and reproductive barriers restrict gene flow into the nascent hybrid species. We propose that an origin of hybrid species where the hybrid lineage gets geographically isolated from its parental species, as seems to have happened in this system, might be more common in nature than previously assumed.

Physiological effects of climate on distributions of endothermic species

Aim Determining the mechanisms underlying climatic limitation of species distributions is essential for understanding responses to current climatic change. Disentangling direct (e.g. physiological) and indirect (e.g. trophic) effects of climate on distributions through occurrence-based modelling is problematic because most species use the same area for both shelter and food acquisition. By focusing on marine birds that breed on land but feed at sea, we exploit a rare opportunity to dissociate direct from indirect climatic effects on endothermic species. Location Coastal Europe. Methods We developed climate-response surfaces (CRS) for 13 seabird species in coastal Europe, linking terrestrial climatic variables considered important for heat transfer with presence/absence data across each species’ entire European breeding range. Agreement between modelled and actual distribution was assessed for jackknifed samples using area under the curve (AUC) of receiver operating characteristic plots. Higher AUC values indicated closer correspondence between observed breeding distribution and terrestrial climate. We assessed the influence of several ecological factors on model performance across species.

Rapid and continued population decline in the Spoon-billed Sandpiper Eurynorhynchus pygmeus indicates imminent extinction unless conservation action is taken

SummaryThe Spoon-billed Sandpiper Eurynorhynchus pygmeus (IUCN Category: Critically Endangered) is in rapid decline. Data from across the entire breeding range (Chukotka and Koryakya in the Russian far north-east) and especially from the well-studied southern core breeding area at Meinypilgyno, confirm the continuing strong decline. At four breeding sites, where more than two counts were available for analysis, the decline was estimated at 26% per annum between 2002 and 2009, or an 88% decline over this period. Allowing for unsurveyed areas, this equates to a decline from a total population of approximately 1,000 breeding pairs in 2000 to 120–220 in 2009. Breeding studies at Meinypilgyno in 2003–2007 (not 2006) showed that the proportion of nests hatching at least one chick was 0.65 and once chicks left the nest, the mean brood size of chicks up to one week old was 1.99. Where it was possible to follow broods, 0.61 chicks fledged per nesting attempt. Survival and recruitment analysis of birds ringed at Meinypilgyno indicated that annual adult survival did not significantly differ over the 2003–2009 study but that recruitment in to the adult breeding population was effectively zero in all but one year of the study (2005). Resighting data for the last two years of the study were sparse due to very low numbers of marked adults being recorded and survival rates over the last 2–3 years of the study must therefore be treated with caution. The analysis therefore indicated that after fledging, survival during immaturity must be very low, leading to a low (or no) recruitment into an ageing population. Recent observations collated from the non-breeding areas confirm the declining trend observed in the breeding areas and imply that the main threats to the population lie along the migration route or in the wintering areas. These are poorly known although hunting in the wintering areas has been identified as a major mortality factor. Other threats include major loss of their intertidal habitats, and collection of birds on the breeding areas by specimen collectors. Improved monitoring in both the breeding and non-breeding areas as well as research on juvenile survival is recommended. Concerted international conservation action is essential if this species is to avoid extinction. This requires (i) improved understanding of the main wintering and staging areas and associated threats; (ii) addressing those threats that can be tackled with immediate effect, such as hunting; (iii) continued long-term monitoring on the breeding areas; (iv) an exploration of other potential breeding areas; (v) conservation action at all important stop-over and wintering sites along the entire flyway and (vi) consideration of a captive-breeding programme to ensure the survival of this species.

Population growth and density, diet and breeding success of striated caracaras Phalcoboenus australis on New Island, Falkland Islands

The striated caracara is a rare and specialised raptor, with a distribution restricted to outer islands of southern South America and the Falklands, where it lives in a unique obligate association with seabirds and seals. Despite its tameness, interesting adaptations and the fact that it is classified as near-threatened, there is virtually no published quantitative information on its demography, ecology and behaviour. We carried out a study on New Island, West Falklands, where the species was eradicated due to heavy persecution up to the 1960s. Recolonisation started after 1972 and presently there are an estimated 85 adult territorial pairs plus ca. 130 non-territorial immatures, representing an overall density of 15.5 striated caracaras per km2. The population is estimated to have increased by 15% per year over the past 3 decades, with the result that New Island now harbours the largest known breeding aggregation on a single island in the entire breeding range of the species. The spring and summer diet of striated caracaras on New Island is dominated by one small seabird, the thin-billed prion Pachyptila belcheri. An estimated 25,000 adult and sub-adult prions are consumed every year, but this possibly represents less than 1% of the local population. The diet of different pairs displayed significant differences, which were probably related to differences in the availability of prey types between territories. Breeding success in recent years was very high, suggesting that conditions are good and the population may not yet have reached the island’s carrying capacity.

Can a ‘wintering area effect’ explain population status of Swainson's hawks? A stable isotope approach

ABSTRACTIt has been suggested that declines in breeding populations of Swainson's hawks (Buteo swainsoni) in California, Oregon, and Nevada may be due to differential mortality of hawks on their wintering grounds. Although massive mortality incidents reported on the wintering grounds partially support this suggestion, there are no data showing differential use of wintering areas by breeding populations of Swainson's hawks. We used stable‐hydrogen isotope analysis of feathers to determine whether large flocks of hawks wintering in Argentina consisted of a mixture of individuals from across the North American breeding range or consisted of individuals from discrete breeding populations. We found that flocks of wintering Swainson's hawks consisted of a mixture of individuals. The lack of connectivity between populations of breeding and wintering hawks suggests that high wintering mortality, either natural or human‐induced, is unlikely to have direct consequences on a single breeding area in North America. The demographic effects of winter mortality should be ‘diluted’ across the entire breeding range of Swainson's hawks.

What genetics tell us about the conservation of the critically endangered Balearic Shearwater?

The Balearic shearwater Puffinus mauretanicus is one of the most critically endangered seabirds in the world. The species is endemic to the Balearic archipelago, and conservation concerns are the low number of breeding pairs, the low adult survival, and the possible hybridization with a sibling species, the morphologically smaller Yelkouan shearwater ( P. yelkouan). We sampled almost the entire breeding range of the species and analyzed the genetic variation at two mitochondrial DNA regions. No genetic evidence of population decline was found. Despite the observed philopatry, we detected a weak population structure mainly due to connectivity among colonies higher than expected, but also to a Pleistocene demographic expansion. Some colonies showed a high imbalance between immigration and emigration rates, suggesting spatial heterogeneity in patch quality. Genetic evidence of maternal introgression from the sibling species was reinforced, but almost only in a peripheral colony and not followed, at least to date, by the spread of the introgressed mtDNA lineages. Morphometric differences were not correlated with mtDNA haplotypes and introgression is probably due to a secondary contact between the two species several generations ago. Overall, results suggested that the very recent demographic decline in this critically endangered species has not yet decreased its genetic variability, and connectivity found among most colonies should help to reduce species extinction risk. Spreading of introgression should be monitored, but the species is not jeopardized at the moment by genetic factors and the major conservation actions should concentrate at enhancing adult survival.

PREDICTING PRESENCE-ABSENCE OF THE ENDANGERED GOLDEN-CHEEKED WARBLER (DENDROICA CHRYSOPARIA)

Abstract The golden-cheeked warbler (Dendroica chrysoparia) is a federally endangered, Neotropical migrant songbird that breeds exclusively in central Texas. Previous studies have identified habitat characteristics associated with the warbler, but a predictive model incorporating data collected over the entire breeding range is lacking. Using logistic regression, we constructed models at 2 scales based on vegetational and topographical data from individual survey points (local-scale) and potential habitat patches (landscape-scale). Models identified similar characteristics important in predicting golden-cheeked warbler occupancy, despite a difference in scale. The models suggested that warbler occupancy was positively associated with steep slopes, forest interior, Ashe juniper (Juniperus ashei) canopy cover, a tall canopy, and proximity to protected lands.

Siblicidal brood reduction in South Polar Skuas

Siblicide in the South Polar Skua (Catharacta maccormicki) was studied at Cape Crozier, Ross Island, Antarctica during the 1993/94 austral summer. Sixty‐six two‐egg nests were monitored, providing 49 two‐chick broods for study. Eighteen pairs of chicks (37% of broods) were raised. Single chicks survived in 27 nests, of which 26 were first chicks. Only three second chicks outlived firsts in the same brood, of which only one survived to at least 20 days. Attacks began within the first days of the second chick hatching. Second chicks were lost or evicted from the nest area on average 3.05 ± 0.5 days (mean ± SE) after hatching. Although first and second chicks had almost identical body masses at hatching (68.3 ± 4.7 g versus 69.9 ± 5.6 g), first chicks weighed 102.3 ± 4.2 g when the second hatched. At the peak of attacks at 48 h after the second hatched, first chicks weighed 146.5 ± 4.7 g on average and seconds only 83.3 ± 1.8 g. Between‐brood differences in mass and age of chicks in different broods had minimal influence on either the intensity of sibling aggression or its outcome. First chick aggression towards the second persisted for at least 3 weeks in broods kept separately in enclosures at the nest. All attacks began near the nest, usually at chick feeding. Parents intervened in a high proportion of attacks, invariably in pecking attacks, but did not halt them in the longer term. Twelve of 26 second chicks survived for a time elsewhere on the territory or were adopted by neighbours after being evicted from the nest area. Brood reduction through siblicide in this species is a two‐phase process: eviction from the nest area, followed by death from predation, exposure or starvation. A review of the literature showed that varying levels of siblicide occur throughout the entire breeding range of the South Polar Skua, and, except for some possible records for the Brown Skua, is uniquely confined to this species within the Stercorariidae. We concluded that brood reduction through siblicide is facultative, its intensity in each population each season determined by local foraging conditions.