Journal of Avian Biology最新文献

{"title":"Microclimate shifts in nest-boxes and natural cavities throughout reproduction","authors":"Joanna Sudyka,&nbsp;Irene Di Lecce,&nbsp;Marta Szulkin","doi":"10.1111/jav.03000","DOIUrl":"10.1111/jav.03000","url":null,"abstract":"<p>Animals breeding in nest-boxes experience nesting environments in which they did not originally evolve. Despite the central importance of nesting microclimate for offspring fitness, little is known about the thermal properties of human-provided nest sites compared to natural ones. In particular, comparisons with offspring in the nest are lacking. Here, we compare microclimate (temperature and absolute humidity) from the onset of breeding, thus starting with nest-site choice and ending with the post-fledging stage, quantified in natural cavities and nest-boxes used by several species of hollow-nesting birds in a temperate deciduous forest. We confirm that across all nesting stages, nest-boxes were thermally unstable when compared to natural cavities, with higher temperature maximums, larger amplitudes and worse insulation from maximum ambient temperatures relative to natural cavities. Surprisingly, as average humidity of natural cavities was previously shown to be higher than in nest-boxes, in the presence of actively thermoregulating young, nest-boxes were more humid than natural cavities. When offspring were in the nest, internal microclimatic shifts were mitigated three times more effectively in natural cavities than in nest-boxes (in terms of mean daily differences from ambient temperature). Artificial cavity microclimate is likely to amplify the adverse effects of projected temperature increases by compromising thermoregulation of developing animals. We stress that conservation efforts should focus on the protection of areas offering natural breeding-hollows to reduce the potential impacts of climate change on breeding animals.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2022-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jav.03000","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44463283","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Extra-pair paternity correlates with genetic diversity, but not breeding density, in a Neotropical passerine, the black catbird","authors":"Joshua B. LaPergola,&nbsp;Christina Riehl,&nbsp;Juan E. Martínez-Gómez,&nbsp;Blanca Roldán-Clarà,&nbsp;Robert L. Curry","doi":"10.1111/jav.03034","DOIUrl":"10.1111/jav.03034","url":null,"abstract":"<p>The frequency of extra-pair paternity (EPP) varies widely across socially monogamous birds, but the proximate mechanisms driving this variation remain unclear. In this study, we tested two major factors hypothesized to influence extra-pair mating – breeding density and genetic diversity – by comparing genetic mating patterns in two populations of black catbirds <i>Melanoptila glabrirostris</i>. This Neotropical songbird is endemic to the Yucatán Peninsula, including eastern Mexico, and its offshore islands. We sampled one mainland (Sian Ka'an Biosphere Reserve) and one island (Isla Cozumel) population and used single-nucleotide polymorphisms (SNPs) to quantify heterozygosity and genetic parentage over two breeding seasons. Moderate levels of EPP occurred in both populations (9.5–35% of offspring and 17–45% of nests). Contrary to predictions, breeding density did not affect EPP: although breeding densities were much higher on the mainland than on the island, EPP rates did not differ between populations, and local breeding density was not correlated with EPP at individual nests. In contrast, partial support emerged for the hypothesis that genetic diversity influences EPP: extra-pair offspring were more heterozygous than within-pair offspring. However, the two populations did not differ in genetic diversity, and neither the heterozygosity of social fathers nor within-pair relatedness predicted EPP. These results are consistent with recent comparative studies suggesting that breeding density is not a critical driver of EPP rates, and that not all tropical songbirds exhibit low rates of EPP.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2022-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jav.03034","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47591217","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Interactive effects of arrival date, territory quality and male polyterritorial behaviour on the mating system of the sedge warbler Acrocephalus schoenobaenus: a path analysis","authors":"Wojciech Bielański,&nbsp;Adam M. Ćmiel,&nbsp;Tadeusz A. Zając","doi":"10.1111/jav.02899","DOIUrl":"10.1111/jav.02899","url":null,"abstract":"<p>Classical models predict that male fitness is based on resources monopolized and invested in reproduction, and/or on individual quality providing offspring with sexually attractive traits or viable genes. However, these factors are frequently correlated, making their relative influence on male fitness difficult to describe and quantify. We analysed the relative influence of the main features of the sedge warbler's <i>Acrocephalus schoenobaenus</i> breeding system, i.e. age, arrival date, territory quality, male sexual activity (song and polyterritorial behaviour), on males' mating success, fledging success and local recruitment. Results show that this species' breeding system involves three main paths: 1) earlier-arriving males have higher mating success, regardless of territory quality, 2) the quality of territories pre-empted by earlier males directly influences recruitment and 3) mating success is influenced by male sexual activity (polyterritorial behaviour), but an additional territory also affects recruitment directly. As arrival date plays a significant role in all the paths, the whole system seems to depend on male quality; although the benefits accruing to male fitness are obtained not only through sexual selection but also through resource monopolization.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2022-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jav.02899","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49134281","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Competition between the black-winged kite and Eurasian kestrel led to population turnover at a subtropical sympatric site","authors":"Kuan-Hao Chen,&nbsp;Wen-Loung Lin,&nbsp;Si-Min Lin","doi":"10.1111/jav.03040","DOIUrl":"10.1111/jav.03040","url":null,"abstract":"<p>Population expansion of the black-winged kite <i>Elanus caeruleus</i> has been a global trend in recent decades. Since first recorded in Taiwan in 2001, they rapidly occupied plains areas of this subtropical island which has led to interspecific competition with the wintering Eurasian kestrel <i>Falco tinnunculus</i>. In this study, we analyzed historical surveys to estimate the population trends of both species in Taiwan. We then used Pianka's index to quantify the degree of niche overlap based on diet composition and foraging peaks. Finally, we designed an experiment to test the aggressiveness of the two raptors when facing conspecific or heterospecific intruders. Airport avifauna survey (2002–2017) data from eight different airports and eBird data (2000–2019) from 21 hotspot grids both showed population turnover between the two raptors, with a decline in the wintering Eurasian kestrel and an expansion of the black-winged kite. Rodents were the largest share of prey for both species, indicating that the two raptors have a high degree of niche overlap (an overlap index of 0.74 by prey frequency, 0.97 by prey biomass and 0.89 by foraging time). The black-winged kite exhibited higher boldness and aggressiveness toward intruders, with its aggressiveness toward kestrel specimens (2.9 ± 2.4 strikes) significantly higher than that toward kite specimens (1.1 ± 1.8 strikes). Attacks by the black-winged kite may have prompted the Eurasian kestrel to choose other wintering grounds. As a result, the number of wintering kestrels decreased, leading to opposing population trends of the two species.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2022-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jav.03040","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44899120","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Nest-boxes alter the reproductive ecology of urban cavity-nesters in a species-dependent way","authors":"Joanna Sudyka,&nbsp;Irene Di Lecce,&nbsp;Lucyna Wojas,&nbsp;Patryk Rowiński,&nbsp;Marta Szulkin","doi":"10.1111/jav.03051","DOIUrl":"https://doi.org/10.1111/jav.03051","url":null,"abstract":"<p>Human-provided nesting shelters such as nest-boxes mitigate the shortage of natural breeding sites. Since artificial nests are not where animals evolved and optimised their reproductive performance, it remains inconclusive if these are adequate substitutes, ensuring equivalent fitness returns while breeding. In particular, most knowledge on the ecology of cavity-nesting birds comes from nest-box populations, but no study has directly compared fitness consequences of breeding inside nest-boxes in relation to natural cavities in cities. We directly compare the reproductive performance, life-history trait variation and fitness consequences for two small passerines, blue and great tits, breeding in nest-boxes as opposed to natural cavities in an urban deciduous forest. We use a quasi-experimental setting to comprehend the conservation potential of these artificial cavities and to support/question generalisations stemming from nest-box studies. We show that the effects of cavity type vary between species: in blue tits, fitness proxies were negatively affected by nest-boxes (lower fledging success and fledgling numbers, longer time spent in the nest and later fledging date relative to natural cavities), while in great tits, the fitness proxies were unaffected by cavity type. Importantly, we detected accelerated incubation in both species breeding in nest-boxes. No differences in pre-hatching traits (lay date, clutch size, hatching rates) between cavity types suggest that the fitness deterioration occurred because of post-hatching effects. We highlight the ecological importance of old-growth tree stands, providing natural cavities for city-breeding animals and the need for quantifying alterations of reproductive ecology in other taxa using human-provided nests. Owing to the detected cavity type-dependent variation in reproductive performance, we support the criticism regarding the unconditional extrapolation of evolutionary and ecological interpretations of nest-box studies to general populations.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2022-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jav.03051","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"137865753","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reproductive success of the wood warbler Phylloscopus sibilatrix varies across Europe","authors":"Nino Maag,&nbsp;Malcolm D. Burgess,&nbsp;Marta Maziarz,&nbsp;Shannon Lüpold,&nbsp;John W. Mallord,&nbsp;Richard K. Broughton,&nbsp;Andrew Cristinacce,&nbsp;Raphaël Arlettaz,&nbsp;Sandro Carlotti,&nbsp;Joan Castello,&nbsp;Tony Davis,&nbsp;Michael Gerber,&nbsp;Alex Grendelmeier,&nbsp;Christopher J. Orsman,&nbsp;Michael Riess,&nbsp;Pablo Stelbrink,&nbsp;Tomasz Wesołowski,&nbsp;Zephyr Züst,&nbsp;Gilberto Pasinelli","doi":"10.1111/jav.03033","DOIUrl":"10.1111/jav.03033","url":null,"abstract":"<p>Differences in population trends across a species' breeding range are ultimately linked to variation in demographic rates. In small songbirds, demographic rates related to fecundity typically have strong effects on population trends. Populations of a forest songbird, the wood warbler <i>Phylloscopus sibilatrix</i>, have been declining in many but not all regions of the European breeding range. We investigated if clutch size, hatching rate, nest survival and number of fledglings vary across Europe, and if nest survival is related to differences in the regionally dominant nest predator class (birds versus mammals). From 2009 to 2020, we monitored 1896 nests and used cameras at a subsample of 645 nests in six study regions: the United Kingdom (mid-Wales, Dartmoor, the New Forest), Germany (Hessen), Switzerland (Jura mountains) and Poland (Białowieża National Park). Number of fledglings was lowest in the New Forest (1.43 ± CI 0.23), intermediate in Jura (2.41 ± 0.31) and Białowieża (2.26 ± 0.24) and highest in mid-Wales (3.02 ± 0.48) and Dartmoor (2.92 ± 0.32). The reason for low reproductive success in the New Forest, Jura and Białowieża was low nest survival, and large clutch sizes in Białowieża did not compensate for high nest losses. High reproductive success in mid-Wales and Dartmoor was due to high nest survival and large clutch sizes. Overall predation rates were similar everywhere despite variation between the regions in the dominant nest predator class. Unsuccessful nests in mid-Wales were mainly predated by birds; in Dartmoor, the New Forest, Hessen and Jura similarly by birds and mammals; and in Białowieża exclusively by mammals. Regional reproductive success does not match the population trends recently reported for the wood warbler in the six study regions (i.e. high reproduction ≠ positive trend). Annual survival may be a decisive factor, but it is difficult to quantify for a nomadic species such as the wood warbler that rarely returns to the same breeding locations.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2022-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jav.03033","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43749905","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sea crossings of migratory pink-footed geese: seasonal effects of winds on flying and stopping behaviour","authors":"Jan Geisler,&nbsp;Jesper Madsen,&nbsp;Bart A. Nolet,&nbsp;Kees H. T. Schreven","doi":"10.1111/jav.02985","DOIUrl":"10.1111/jav.02985","url":null,"abstract":"<p>Migratory birds may need to cross barriers such as seas, without opportunities to rest or refuel. Waterbirds, unlike land birds, can stop at sea to rest or wait for better winds and thus may be less selective for supportive winds at departure and tolerate larger drift. However, pay-offs of waiting are likely to depend on circumstances (e.g. pressure for well-timed arrival, wind availability and travelling with/without juvenile brood), thus migratory behaviour during barrier crossings is expected to differ between seasons. We studied pink-footed geese <i>Anser brachyrhynchus</i> crossing the Barents Sea (ca 650 km), in spring and autumn during 2018–2020, using 94 GPS-tracks of 38 individuals, with annotated ERA5 weather data. We found that 1) especially in autumn, geese selected supportive winds for departure; 2) in spring, geese experienced lower wind support and more crosswinds than in autumn, leading to 23% longer routes, 60% longer durations, 93% longer air distances and 45% higher ratios of air-to-ground distances; 3) in both seasons, geese had more tailwinds in the first part of crossings, and in spring when deviating more from the shortest route; 4) geese stopped at sea more often in spring (mean 11×) than autumn (3×), in spring during earlier stages of crossings, but in both seasons, spent half of the crossing time at sea, during which they still continued to approach their destination slowly; 5) stops at sea happened mostly in adverse winds, warmer air, higher air humidity and on calmer water and, in autumn, took longer without juvenile brood. We conclude that for migrating pink-footed geese, Arctic capital breeders, the importance of time and energy can shift en route and that seasonal differences in wind support, flying and stopping behaviour and the pressure for a well-timed arrival cause the Barents Sea to be a larger barrier in spring than in autumn.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2022-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jav.02985","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44580917","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Congeneric predators fill discrete niches created by the relative abundances of their prey species","authors":"Eliot T. Miller,&nbsp;Oisin Mac Aodha,&nbsp;Emma I. Greig,&nbsp;David N. Bonter,&nbsp;Wesley M. Hochachka","doi":"10.1111/jav.02934","DOIUrl":"10.1111/jav.02934","url":null,"abstract":"<p>To what degree is niche partitioning driven by underlying patterns in resources such as food, rather than by competition itself? Do discrete niches exist? We address these questions in the context of Cooper's and sharp-shinned hawks, two broadly sympatric, North American, bird-eating raptors in the genus <i>Accipiter</i>. We find that the resource base, as quantified by body masses of birds at bird feeders, is approximately lognormal (smallest birds are most abundant), with lesser modes (peaks) in abundance at larger body mass. The predators appear to exploit peaks in the resource base, with sharp-shinned hawks focusing on small prey items (median of 26.5 g), and Cooper's hawks taking prey from the two most abundant peaks (both the small body mass peak and a lesser peak at medium body mass ~90 g). We tested the ability of citizen scientists to distinguish these notoriously similar species, and we determined the influence of potential false positive detections on our conclusions. We find that citizen scientists struggle to distinguish these predators from one another, and 18% of Cooper's hawks were identified as sharp-shinned hawks, while 27% of sharp-shinned hawks were identified as Cooper's hawks. Yet, simulations show that this uncertainty did not jeopardize our qualitative conclusions.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2022-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jav.02934","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46352706","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dynamic body acceleration improves mapping of at-sea foraging behavior in black-tailed gulls Larus crassirostris","authors":"Rui Ma,&nbsp;Kentaro Kazama,&nbsp;Yogi C. Yasutake,&nbsp;Mami T. Kazama,&nbsp;Shota Tsukamoto,&nbsp;Yutaka Watanuki","doi":"10.1111/jav.02869","DOIUrl":"10.1111/jav.02869","url":null,"abstract":"<p>Areas at which seabirds forage intensively can be discriminated by tracking the individuals' at-sea movements. However, such tracking data may not accurately reflect the birds' exact foraging locations. In addition to tracking data, gathering information on the dynamic body acceleration of individual birds may refine inferences on their foraging activity. Our aim was to classify the foraging behaviors of surface-feeding seabirds using data on their body acceleration and use this signal to discriminate areas where they forage intensively. Accordingly, we recorded the foraging movements and body acceleration data from seven and ten black-tailed gulls <i>Larus crassirostris</i> in 2017 and 2018, respectively, using GPS loggers and accelerometers. By referring to video footage of flying and foraging individuals, we were able to classify flying (flapping flight, gliding and hovering), foraging (surface plunging, hop plunging and swimming) and maintenance (drifting, preening, etc.) behaviors using the speed, body angle and cycle and amplitude of body acceleration of the birds. Foraging areas determined from acceleration data corresponded roughly with sections of low speed and area-restricted searching (ARS) identified from the GPS tracks. However, this study suggests that the occurrence of foraging behaviors may be overestimated based on low-speed trip sections, because birds may exhibit long periods of reduced movement devoted to maintenance. Opposite, the ARS-based approach may underestimate foraging behaviors since birds can forage without conducting an ARS. Therefore, our results show that the combined use of accelerometers and GPS tracking helps to adequately determine the important foraging areas of black-tailed gulls. Our approach may contribute to better discriminate ecologically or biologically significant areas in marine environments.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2022-08-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jav.02869","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45178075","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Interspecific competition and facilitation coexist in mixed-species bird flocks of montane coniferous forests in Taiwan","authors":"Chao-Chieh Chen,&nbsp;Chun-Chieh Liao,&nbsp;Bruno Andreas Walther","doi":"10.1111/jav.02947","DOIUrl":"10.1111/jav.02947","url":null,"abstract":"<p>Besides competition, positive interactions also play an important role in shaping the social structure of mixed-species bird flocks. This study aimed to illuminate the interspecific interactions of competition and facilitation in mixed-species bird flocks. We recorded the foraging behavior and microhabitat use of flocking species in montane coniferous forests of Taiwan under different social contexts. Foraging niche breadth and niche-overlap with other flocking species were compared between individuals inside and outside of mixed flocks. For the three microhabitat variables (foraging locations, vertical strata and horizontal strata), relationships between niche-overlaps of heterospecific pairs of these flocking species and their corresponding interspecific associations were determined using a simple linear regression. While in mixed flocks, two understory species, Taiwan fulvetta <i>Fulvetta formosana</i> and yellowish-bellied bush warbler <i>Horornis acanthizoides</i>, shifted their foraging from shrubs upwards into coniferous trees. Meanwhile, flamecrests <i>Regulus goodfellowi</i> moved downwards vertically within the canopy, and black-throated tits <i>Aegithalos concinnus</i> spread out horizontally along branches. In addition, flamecrests applied many more sally-hovers inside of mixed flocks than outside of flocks. All four species are insectivores which might find it more difficult to obtain sufficient food during the colder winters when food resources become scarcer. Therefore, they may be using the increased vigilance afforded by the flock to expand their foraging niches and thus to increase their foraging opportunities inside mixed flocks. Furthermore, niche-overlaps of heterospecific pairs of the 11 common flocking species were positively correlated with their corresponding interspecific associations on all three microhabitat variables. These results indicate that a greater foraging niche-overlap between two flocking species would result in higher coexistence of the two species in mixed flocks. Consequently, facilitative interactions occurred in these mixed-species flocks in addition to competitive interactions.</p>","PeriodicalId":15278,"journal":{"name":"Journal of Avian Biology","volume":null,"pages":null},"PeriodicalIF":1.7,"publicationDate":"2022-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/jav.02947","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47397697","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}