Studies providing a detailed diet description of whole-bird communities are surprisingly scarce. Yet, these studies are pivotal to comprehend the mechanisms structuring communities and the ...persistence of each species in the ecosystem. We characterized the diet of a shorebird community in a key non-breeding area of the East Atlantic Flyway, the Bijagós Archipelago (West Africa), combining molecular and morphological prey identification based on 239 droppings from 15 species. Our results show that while relying upon a super-abundant prey (fiddler crab), shorebirds consumed a very high number of taxa. We stress the relevance of highly mobile prey (especially crustaceans but also fish), which typically appear to be of little importance in most shorebird studies. Our results suggest that by consuming a high diversity of prey, shorebirds may reduce competition. This may be critical in a site ranked as the second most important area in West Africa for migratory shorebirds but marked by low benthic invertebrate availability. We further compared the performance of DNA metabarcoding and morphological identification of prey. Overall, molecular and morphological methods combined delivered the most comprehensive results, although molecular methods largely surpassed morphological methods regarding taxonomic detail achieved and number of prey taxa found (4 times more). Taxonomic resolution in the identification of polychaetes and bivalves using the 16S primer was low (mostly to class), whereas this primer clearly performed better than mitochondrial cytochrome c oxidase in identifying more insects and fish. We emphasize the need to increase invertebrate representatives from West Africa in barcode databases, in order to enhance metabarcoding results.
In the north Atlantic, rocky intertidal shores with diverse macroalgal assemblages are common. Despite this, the effect of macroalgae on bird use of these habitats is not well understood. We used a ...single-season, single-species occupancy framework to investigate the influence of the macroalgal assemblage on 3 bird guilds and 2 single-species groups: shorebirds (waders), scavengers, divers, common eider
Somateria mollissima
non-parenting adults, and common eider broods. In particular, we considered whether bird occupancy is more strongly determined by the taxonomic composition of the macroalgal assemblage or by structural characteristics of the collective assemblage. We conducted avian point counts and intertidal habitat surveys at 75 sites along the Maine (USA) coast in 2016 and 2017. Macroalgae increased the probability of site occupancy for 1 guild and 2 single-species groups. Most notably, we found that shorebird occupancy had a positive relationship with the spatial extent and mat depth of
Ascophyllum nodosum
, indicating a preference for more homogeneous and deeper macroalgal assemblages dominated by this common, tall-canopied taxon. In contrast, common eider presence had a positive relationship with the spatial extent of 2 categories of shorter-canopied macroalgae that are less dominant members of the macroalgal assemblage. Both shorebirds and eiders were less likely to occur in areas with steeper intertidal slopes, which provide less potential habitat during low tides. Overall, our results suggest that macroalgae composition and availability influences bird occupancy in rocky intertidal habitats, but more mechanistic studies (e.g. behavioral) are needed to understand the exact role macroalgae play in coastal bird ecology.
Abstract We analysed primary and secondary feather moult and fat reserves in 539 Common Snipes captured in the middle Pripyat River Valley, an important stopover site for waders in Central Europe, ...between 2002 and 2022. The average daily rate of feather growth was 1.89% in primaries and 2.27% in secondaries, being one of the highest documented in waders. The estimated duration of growth for a single flight feather varied from 11 to 21 days in primaries and from 8 to 11 days in secondaries. Moreover, multiple flight feathers (up to 14) were replaced simultaneously. As a result, the wing moult in Common Snipes was rapid with the mean primary moult duration estimated at 53 days (28 June–20 August) according to the Underhill–Zucchini model, and only 20 days in secondaries (31 July–20 August) based on moult estimates of individual secondaries. Hence, although secondary feathers began to grow when primary moult was already advanced, moulting of both flight feather groups was completed in most birds at almost the same time. Our study shows that Common Snipe in the middle Pripyat River Valley exhibit very rapid wing moult with large wing gaps. Fat reserves and thus body mass of Common Snipes were the lowest when the wing gap was greatest, compensating for their reduced wing area. Late and slow movement towards wintering grounds, allows them to moult rapidly at the early stage of autumn migration, which is likely to occur only in sites with abundant food resources.
Zusammenfassung Schnelle Schwungfedermauser und Fettreserven bei der Bekassine Gallinago gallinago zu Beginn des Herbstzuges Wir analysierten die Mauser der primären und sekundären Schwungfedern sowie die Fettreserven von 539 Bekassinen, die zwischen 2002 und 2022 im mittleren Tal des Flusses Pripjat gefangen wurden, einem wichtigem Rastgebiet für Watvögel in Mitteleuropa. Die durchschnittliche tägliche Wachstumsrate der primären Schwungfedern betrug 1,89% und die der sekundären Schwungfedern 2,27%, eine der höchsten Wachstumsraten, die bei Watvögeln bisher dokumentiert wurden. Die geschätzte Wachstumsdauer für einzelne primäre Schwungfedern variierten zwischen elf und 21 Tagen und für sekundäre Schwungfedern zwischen acht und elf Tagen. Außerdem wurden mehrere Schwungfedern (bis zu 14) gleichzeitig erneuert. Nach dem Underhill-Zucchini-Model verlief die Flügelmauser bei den Bekassinen also sehr schnell, mit einer geschätzten durchschnittlichen Mauserdauer von 53 Tagen (28. Juni bis 20. August) für primäre Schwungfedern und nur 20 Tagen (31. Juli bis 20. August) für sekundäre Schwungfedern. Obwohl die sekundären Schwungfedern erst zu wachsen begannen, als die Mauser der primären Schwungfedern bereits weit fortgeschritten war, wurde die Mauser der beiden Flugfedergruppen bei den meisten Individuen fast gleichzeitig abgeschlossen. Unsere Studie zeigt, dass Bekassinen im mittleren Tal des Flusses Pripjat eine schnelle Flügelmauser mit großen Lücken in den Flügeln vollziehen. Die Fettreserven und damit die Körpermasse der Bekassinen waren am geringsten, als die Lücken im Flügel am größten waren, um die verringerte Flügelfläche zu kompensieren. Späte und langsame Zugbewegungen in Richtung der Überwinterungsgebiete ermöglichen es den Bekassinen, zu Beginn des Herbstzuges schnell zu mausern, was wahrscheinlich nur dort geschieht, wo es reichliche Nahrungsressourcen gibt.
We report new records of the Dot-winged Crake Porzana spiloptera in southern Chile, an almost unknown species distributed mainly in Argentina and recently discovered in Chile. The occasional capture ...of a juvenile of the species at Cruces River wetland (39°S), and the analysis of sound recordings obtained to explore the acoustic attributes of urban wetland soundscapes, made it possible to discuss the status of the Pacific populations of the species. The new records show that P. spiloptera has a resident status and suggest that the presence of the species in Chile went historically unnoticed, and that it has been confused with the Black Rail Laterallus jamaicensis. Comprehensive surveys and dedicated research that provide fundamental biological aspects such as the current distribution, population abundance, habitat requirements, and main threats for these secretive rails are urgently needed for their conservation.
Competition intensity depends on the number of competitors and the amount of resources available. Coexistence of potential competitors can be enabled through niche differentiation or high resource ...availability. Using diet analysis, we investigated which of these 2 mechanisms was in play for coexisting shorebirds at a major staging site in the northern Yellow Sea, China, during northward migration in 2011 and 2012. Competition for food at this site is expected to be intense, with an estimated 250,000 migratory shorebirds gathering annually to refuel over a short period. Great Knots (Calidris tenuirostris), Eurasian Oystercatchers (Haematopus ostralegus osculans), and Red Knots (C. canutus) selected mostly the bivalve Potamocorbula laevis, whereas Bar-tailed Godwits (Limosa lapponica) had a broader diet and showed selection for polychaetes, even though most of their biomass intake was of P. laevis. Although all of these shorebirds fed on P. laevis, they showed different size selection and used different feeding methods. Bar-tailed Godwits, Great Knots, and Red Knots mainly swallowed P. laevis whole and preferred medium-sized P. laevis with relatively high ratios of flesh content to shell mass. By contrast, Eurasian Oystercatchers stabbed open P. laevis, ingested only the flesh, and preferred large P. laevis that provided the highest energetic return per prey taken. Despite evidence of niche differentiation in prey selection, the diets between the numerically dominant Bar-tailed Godwits and Great Knots overlapped substantially. Their coexistence seems to be enabled by high resource availability rather than niche separation.
The regularization of the wintering status of the Jack Snipe (Lymnocryptes minimus) in NW Italy has been confirmed for the first time within the heathland of the “Baraggia di Candelo Natural Reserve” ...(Piedmont, Biella). Regular monitoring from winter 2009/2010 to winter 2015/2016 allowed to describe the phenology and the abundance of the species in the area comparing it with that of an ally species, the Common Snipe (Gallinago gallinago). A maximum count of 6 birds during winter and at least 13 individuals during the spring migration were recorded. The species was more abundant during the second 10-day period of November and the first 10-day period of March. Jack Snipe outnumber the Common Snipe throughout the period they were censused.
Animals often face a trade‐off between food acquisition and predation/disturbance avoidance. Yet, the extent to which this trade‐off is affected by modulating factors such as thermal risk and ...foraging opportunities has been largely overlooked.
Here, we examined the influence of temporal and environmental gradients on the flight initiation distance (FID, the distance at which animals flee from an approaching human‐simulated predator) and escape mode (flying/low risk versus running/low cost) in 16 species of shorebirds foraging on tidal flats of the Bijagós Archipelago, Guinea‐Bissau. We measured escape responses throughout the low tide period during wet and dry seasons and simultaneously recorded microclimate variables and occurrence of heat‐reduction behaviour (ptiloerection). Furthermore, we measured corticosterone metabolites (CORTm) from droppings in red knots Calidris canutus to assess whether ptiloerection is associated to a physiological stress response to hot conditions.
Overall, birds tolerated a closer approach at higher environmental temperatures and when showing ptiloerection. They also had shorter FIDs during the dry season and towards the start/end of the low tide period. FIDs also increased with body mass and decreased in areas with more human presence. In red knots, individuals showing ptiloerection had higher levels of CORTm, demonstrating a link between physiological and behavioural stress coping responses to heat events.
Our results suggest that heat‐stressed shorebirds take greater risks, supporting the idea of a thermoregulation–predation risk trade‐off. They also indicate that shorebirds adjust risk taking to tidal and seasonal cycles, generally reducing FIDs when the energetic costs of escape are expected to be large. Finally, they suggest that shorebirds habituate to non‐lethal human presence and respond to perceived predation risk in accordance with the predictions of optimal escape theory.
These results are relevant to many animals that face a tight window for foraging activity while being exposed to predation/disturbance and heat during the day. We discuss management implications of our results in the context of global change.
Read the free Plain Language Summary for this article on the Journal blog.
Resumo
Frequentemente os animais são obrigados a estabelecer um compromisso (trade‐off) entre a obtenção de alimentos e a prevenção de predação/perturbação. Fatores externos, como o risco térmico e as oportunidades de alimentação, podem afectar esse compromisso, mas a importância desses potenciais fatores não é conhecida.
Neste estudo, investigámos a influência de gradientes temporais e ambientais sobre a distância de iniciação de voo (FID, a distância a que uma ave foge quando uma pessoa se aproxima simulando um predador) e o modo de fuga (voo/baixo risco versus corrida/baixo custo) em 16 espécies de aves limícolas que se alimentam nas áreas entre‐marés do Arquipélago dos Bijagós na Guiné‐Bissau. As respostas de fuga das aves foram medidas durante o período de baixa‐mar na estação das chuvas e na estação seca. Simultaneamente, foram registadas variáveis microclimáticas, bem como a ocorrência de comportamento de redução de calor (ereção das penas ou ptiloereção) por parte das aves. Com o objetivo de investigar se a ereção das penas é uma resposta ao stress fisiológico causado pelo calor, foram quantificados os metabolitos de corticosterona (CORTm) em dejectos de seixoeiras Calidris canutus.
De um modo geral, as aves toleraram uma maior aproximação em condições de temperatura ambiente mais elevada e quando exibiram ptiloereção. Também se registaram FIDs menores durante a estação seca e nos momentos iniciais ou finais do período de baixa‐mar. A FID aumentou com a massa corporal das aves e diminuiu em áreas com maior presença humana. As aves com comportamento de ptiloereção toleraram uma aproximação maior, e a FID foi menor durante a estação seca. Nas seixoeiras, os indivíduos com ptiloereção registaram maiores niveis de CORTm, sugerindo uma ligação entre o stress fisiológico e comportamental na resposta ao calor.
Os nossos resultados mostram que as aves limícolas sujeitas a stress térmico aceitam maiores riscos, o que sugere a existência de um compromisso entre a termoregulação e o risco de predação. Os dados indicam ainda que as aves ajustam a exposição ao risco de predação aos ciclos tidais e sazonais, diminuindo a FID quando os custos energéticos da fuga são, expectavelmente, mais elevados. Finalmente, os resultados mostram também que as aves limícolas tendem a habituar‐se à presença humana e respondem à percepção de risco de predação de acordo com as predições da ‘teoria da fuga ótima’ (optimal escape theory).
Os resutados deste estudo são relevantes para os animais que só se podem alimentar num período restrito, estando simultaneamente expostos a potencial predação/perturbação e condições de calor elevado. As implicações destes resultados para a conservação são discutidas no contexto das alterações globais.
Read the free Plain Language Summary for this article on the Journal blog.
Planting forests is a commonly suggested measure to mitigate climate change. The resulting changes in habitat structure can greatly influence the diversity and abundance of pre‐existing wildlife. ...Understanding these consequences is key for avoiding unintended impacts of afforestation on habitats and populations of conservation concern.
Afforestation in lowland Iceland has been gaining momentum in recent years and further increases are planned. Iceland supports internationally important breeding populations of several ground‐nesting, migratory bird species that mostly breed in open habitats. If afforestation impacts the distribution and abundance of these species, the consequences may be apparent throughout their non‐breeding ranges across Europe and Africa.
To quantify the effects of plantation forests on the abundance and distribution of ground‐nesting birds (in particular waders, Charadriiformes), surveys were conducted on 161 transects (surrounding 118 plantations) perpendicular to forest edges throughout Iceland. The resulting variation in density with distance from plantation was used to estimate the likely changes in bird numbers resulting from future afforestation plans, and to explore the potential effects of different planting configuration (size and number of forest patches) scenarios.
Of seven wader species, densities of five (golden plover Pluvialis apricaria, whimbrel Numenius phaeopus, oystercatcher Haematopus ostralegus, dunlin Calidris alpina and black‐tailed godwit Limosa limosa) in the 200 m surrounding plantations were just under half of those further away (up to 700 m). Redshank Tringa totanus densities were lowest ≤150 m from the plantation edge while snipe Gallinago gallinago densities were 50% higher close to plantations (0–50 m) than further away (51–700 m), and no consistent effects of plantation height, diameter, density or type were identified. Plantations are typically small and widespread, and simulated scenarios indicated that total declines in bird abundance resulting from planting trees in one large block (1,000 ha) could result in only ~11% of the declines predicted from planting multiple small blocks (1 ha) in similar habitats.
Synthesis and application. Planting forests in open landscapes can have severe impacts on populations of ground‐nesting birds, which emphasizes the need for strategic planning of tree‐planting schemes. Given Iceland's statutory commitments to species protection and the huge contribution of Iceland to global migratory bird flyways, these are challenges that must be addressed quickly, before population‐level impacts are observed across migratory ranges.
Útdráttur
Skógrækt er mikilvæg í baráttunni við hnattræna hlýnun en umfangsmiklar breytingar í gróðurfari geta haft mikil áhrif á fjölbreytileika og þéttleika dýra. Mikilvægt er að greina slík áhrif til að komast hjá því að valda óafturkræfum breytingum á dýrastofnum sem hafa hátt verndargildi.
Skógrækt á Íslandi hefur aukist til muna síðustu ár og stefnt er að því að auka hana enn frekar. Á Íslandi eru stórir hlutar heimsstofna ýmissa farfugla sem verpa á jörðu niðri í opnum búsvæðum. Ef aukin skógrækt hefur áhrif á dreifingu og stofnstærðir þessara tegunda, getur áhrifanna gætt á vetrarstöðvum þeirra í Evrópu og Afríku.
Áhrif skóga á þéttleika og dreifingu fugla sem verpa á jörðu niðri (einkum vaðfugla Charadriiformes), voru metin með talningum á 161 sniðum (umhverfis 118 skógarreiti) út frá skógarjöðrum á Íslandi. Tengsl fuglafjölda við fjarlægð frá skógarjöðrum voru notuð til að meta hvernig fjöldi fugla getur breyst með áframhaldandi skógrækt á láglendi Íslands og hvernig þær breytingar eru háðar skipulagi skóga (stærð og fjölda bletta).
Af sjö vaðfuglum var þéttleiki fimm þeirra, heiðlóu Pluvialis apricaria, spóa Numenius phaeopus, tjalds Haematopus ostralegus, lóuþræls Calidris alpina og jaðrakans Limosa limosa, meira en helmingi lægri næstu 200 m við skógarjaðar samanborið við svæði lengra frá skóginum (upp að 700 m). Stelkur Tringa totanus var í lægstum þéttleika næstu 150 m umhverfis skóginn en hrossagaukur Gallinago gallinago fannst hins vegar í hærri þéttleika nálægt skógarjaðrinum (0–50 m) en lengra frá (51–700 m). Engin áhrif fundust af hæð trjáa, stærð og þéttleika skógarreita, eða hvort um barr‐ eða laufskóga var að ræða. Skógarreitir á Íslandi eru almennt litlir og dreifðir, en útreikningar benda til þess að fækkun fugla vegna skógræktar yrði nánast tífalt minni ef 1000 ha skógi yrði plantað í einu lagi miðað við að honum væri plantað í 1 ha reitum.
Samantekt og notagildi. Skógrækt í opnum búsvæðum getur haft mikil áhrif á stofna fugla sem verpa á jörðu niðri og mikilvægt er að hafa það í huga þegar skógrækt er skipulögð. Mikill fjöldi farfugla verpir hér á landi og Ísland hefur skrifað undir alþjóðlega samninga og skuldbundið sig til að vernda þessa fuglastofna. Það er því mikilvægt að huga að áhrifum skógræktar á þessar tegundir og bregðast við þeim áður en áhrifin koma fram á farleiðum íslenskra fugla í Evrópu og Afríku.
Planting forests in open landscapes can have severe impacts on populations of ground‐nesting birds, which emphasizes the need for strategic planning of tree‐planting schemes. Given Iceland's statutory commitments to species protection and the huge contribution of Iceland to global migratory bird flyways, these are challenges that must be addressed quickly, before population‐level impacts are observed across migratory ranges.
Many migratory bird species have undergone recent population declines, but there is considerable variation in trends between species and between populations employing different migratory routes. ...Understanding species‐specific migratory behaviours is therefore of critical importance for their conservation. The Common Sandpiper Actitis hypoleucos is an Afro‐Palaearctic migratory bird species whose European populations are in decline. We fitted geolocators to individuals breeding in England or wintering in Senegal to determine their migration routes and breeding or non‐breeding locations. We used these geolocator data in combination with previously published data from Scottish breeding birds to determine the distributions and migratory connectivity of breeding (English and Scottish) and wintering (Senegalese) populations of the Common Sandpiper, and used simulated random migrations to investigate wind assistance during autumn and spring migration. We revealed that the Common Sandpipers tagged in England spent the winter in West Africa, and that at least some birds wintering in Senegal bred in Scandinavia; this provides insights into the links between European breeding populations and their wintering grounds. Furthermore, birds tagged in England, Scotland and Senegal overlapped considerably in their migration routes and wintering locations, meaning that local breeding populations could be buffered against habitat change, but susceptible to large‐scale environmental changes. These findings also suggest that contrasting population trends in England and Scotland are unlikely to be the result of population‐specific migration routes and wintering regions. Finally, we found that birds used wind to facilitate their migration in autumn, but less so in spring, when the wind costs associated with their migrations were higher than expected at random. This was despite the wind costs of simulated migrations being significantly lower in spring than in autumn. Indeed, theory suggests that individuals are under greater time pressures in spring than in autumn because of the time constraints associated with reproduction.
Protected areas (PAs) are a core component of conservation policy and practice. However, many species for which they are designated are highly mobile, and may move among sites within and beyond PA ...boundaries. Environmental impacts on sites beyond those boundaries could thus impact the PA's protected populations, with the risk of adversely affecting its conservation objectives. Conservationists therefore urgently need tools to assess impacts on PAs and their populations of developments beyond their boundaries. We present a framework for using network analysis of observations of marked individuals to assess the protection footprint of PAs in the wider landscape and the impact footprint of developments within or neighboring PAs. We illustrate the use of this framework by assessing the impact of a current airport development proposal on a partially protected wetland, the Tagus estuary in Portugal, specifically by evaluating the extent of noise disturbance on the PA's population of Black‐tailed Godwits, a protected migratory wader species. By analyzing individual movements between sites and across seasons, we find disturbance impacts on up to 68.3% of individual Black‐tailed Godwits overall, greatly exceeding the estimates of 0.46–5.5% in the airport's Environmental Impact Assessments which derived from count data. We then compared the pre‐development network with simulated networks that represented two levels of site avoidance by removing sites predicted to receive noise in excess of two thresholds, 55 or 65 dB(A). Avoidance by Godwits of the potentially‐impacted sites is predicted to have a larger effect on network structure than removing the same number of sites at random, suggesting that an airport in the proposed location would operate as a barrier to connectivity in this wetland. We also highlight the role that network analyses of locations of marked individuals can play in assessing environmental impacts on protected sites and populations.
Resumo
As áreas protegidas (APs) são uma componente fundamental das políticas de conservação da biodiversidade. Contudo, muitas espécies para as quais estas são estabelecidas são altamente móveis, podendo deslocar‐se entre locais dentro e fora dos limites da AP. Desta forma, os impactes ambientais em locais fora dos limites da AP podem ainda assim afetar as populações que ocorrem dentro da AP, correndo o risco de influenciar adversamente os objetivos de conservação desta. Urge, portanto, desenvolver ferramentas que permitam avaliar os impactes nas APs e nas suas populações, causados por projetos que possam ser desenvolvidos fora dos seus limites. Apresentamos aqui um protocolo que usa análise de redes com base em localizações de animais marcados individualmente, para avaliar a pegada de proteção de APs na paisagem envolvente, e simultaneamente, a pegada de impacte de projetos desenvolvidos dentro ou na proximidade de APs. Demonstramos a utilidade deste procedimento avaliando o impacte de uma proposta de desenvolvimento de um aeroporto numa zona húmida parcialmente protegida, o Estuário do Tejo em Portugal, considerando especificamente a perturbação provocada pelo ruído na população de maçarico‐de‐bico‐direito, uma ave migradora protegida. Analisando os movimentos individuais destas aves entre locais e ao longo das estações, quantificamos impactes por perturbação que podem afetar até 68.3% dos efetivos locais desta espécie no total, um valor muito superior às estimativas indicadas no Estudo de Impacte Ambiental deste projeto (0.46‐5.5%), que tiveram por base dados de contagem. Comparamos também a rede atual (pré‐desenvolvimento) com redes simuladas para dois níveis de perturbação por ruído, 55 e 65 dB(A), simulando a remoção dos locais onde se prevê que irá ocorrer ruído acima desses dois valores, que causam abandono por parte das aves. Prevê‐se que evitar os locais potencialmente impactados tenha um efeito superior na estrutura da rede do que remover o mesmo número de locais aleatoriamente, sugerindo assim que um aeroporto no local proposto funcionaria como uma barreira à conectividade nesta zona húmida. Finalmente, destacamos o papel que a análise de redes com base em localizações de animais marcados individualmente pode desempenhar na avaliação de impactes ambientais em áreas e populações protegidas.
Connectivity between sites can mediate the spatial extent and severity of environmental impacts such as disturbance. In this study, we apply network analysis to a long‐term capture–mark–recapture dataset to evaluate connectivity of the Black‐tailed Godwit population of the Tagus estuary, Portugal, and how it may be altered by a proposed airport development. Our novel method to consider connectivity finds impacts on a far greater proportion of the population than previous studies that used count data alone.
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