Ibis最新文献

The post-fledging dependence period (PFDP) is a fundamental stage in the life cycle of altricial birds that influences their long-term survival and fitness. However, research on the duration of this period in raptors, and on the factors affecting it, is scarce. We performed the first literature review on the length of the PFDP in Accipitridae, the largest family among diurnal raptors, and a meta-analysis examining the effects of breeding latitude and hemisphere, body weight and migratory status, controlling for species phylogeny. Hypotheses were tested at the levels of both species and populations. The length of the PFDP is known for less than half of Accipitridae species, with no data for two-thirds of the threatened and near-threatened species. Larger species and individuals breeding at lower latitudes showed a longer PFDP, as did non-migrants and southern-hemisphere breeders. The effect of latitude was more marked in larger species, in resident populations and in southern-hemisphere breeders. This extended PFDP in larger and tropical raptors may promote juvenile survival. Migration timing and the effects of continentality in the northern hemisphere constrain the PFDP. These findings highlight the importance of encouraging the study of this key, but poorly known, life-cycle stage of raptors.

Stable isotope analysis has been used extensively in migratory bird studies to provide ecological insights that may otherwise be difficult to obtain. However, an understanding of moult is critical for appropriate feather sampling, and here we make the first assessment of its relevance for examining the non-breeding ecology of the Alpine Swift Tachymarptis melba, a long-distance Afro-Palaearctic migrant. We sampled three feather types from birds found dead after their return from migration and investigated variability in δ¹³C, δ¹⁵N and δ²H within and among feathers and between age classes. We found isotopic evidence supporting an interrupted primary moult in adults, with the innermost primary of adults (known to be moulted on the breeding grounds) significantly depleted in ¹³C and ²H compared with either the outermost primary or outermost tail feather, both of which were representative of sub-Saharan non-breeding areas. In contrast, the absence of significant differences in immature birds suggests the probable existence of a non-migratory strategy within this age class. These isotopic insights into moult and life history highlight the potential for stable isotope analysis as a tool for investigating non-breeding strategies in the Alpine Swift.

Investigating the intestinal microbiome and its interactions with the host is crucial for understanding the adaptation mechanisms, functional dynamics and co-evolution of these microbiomes in wild birds. This review examines how gut microbiomes interact with their avian hosts, focusing on the establishment of gut microbiomes, the dynamic changes occurring throughout different life stages and the factors that influence microbial variations. It also explores the evolutionary relationship between birds and their microbial symbionts, and identifies key areas for future research on avian gut microbes to advance wildlife microbiology.

Aapa mires are distinctive base-enriched northern peatland systems, often with pronounced flark-string (deep-pool) surface features. Aapa mires are used by specialist breeding migratory waterbirds (particularly Broad-billed Sandpiper Calidris falcinellus, Jack Snipe Lymnocryptes minimus, Taiga Bean Goose Anser fabalis and Pintail Anas acuta) and support high densities of other nesting wader species (Wood Sandpiper Tringa glareola, Spotted Redshank Tringa erythropus, Ruff Calidris pugnax, Common Snipe Gallinago gallinago, Curlew Numenius arquata and Whimbrel Numenius phaeopus) compared with other peatland landforms. Remote sensing, palynology and peat stratigraphy studies confirm rapid and massive loss of aapa mires through recent drainage, but now also through climate change. Botanists report that recent warming has caused enhanced successional expansions in ombrotrophic raised mire vegetation to engulf aapa mires, destroying their unique surface and nutrient characteristics. As the waterbird species associated with aapa mires cannot survive on acidic base-poor raised mire systems, this ecological change places their populations in jeopardy. While acknowledging the need to reduce climate change through other means, these changes prioritize the need for international cooperation to extend and improve site-safeguarding of intact aapa mires and restoration of damaged aapa mires, as well as effective conservation of affected avian species throughout their full annual cycle to safeguard them, aapa mires and their associated bird communities for future generations. The case regarding aapa mires highlights the need to establish new mechanisms to create cohesive networks of protected areas for special habitats that are of disproportional importance to key avian populations and other wetland species that may not be adequately represented in current site-safeguard networks.

Female investment in reproduction is a critical component of life history that influences both the fitness of the female and her offspring. Oviparous females can allocate energy into egg size and/or clutch size, and this allocation can vary over lifetimes, within populations and among species. However, we know little about whether investment decisions shift within breeding seasons and the factors that influence female reproductive strategies. We studied endogenous and exogenous factors associated with variation in female reproductive investment by measuring 860 eggs from 240 clutches laid by Grasshopper Sparrows Ammodramus savannarum between 2014 and 2019 at the Konza Prairie Biological Station in Manhattan, Kansas, USA. As the breeding season progressed, females laid smaller clutches of heavier eggs, indicating a shift in investment towards fewer but higher quality young. Females that were heavier than expected given their body size laid heavier and larger eggs, but maternal body condition was not related to clutch size. Brood parasitism by Brown-headed Cowbirds Molothrus ater reduced the number of Grasshopper Sparrow eggs in nests, but was unrelated to host egg size or the total number of eggs that a female incubated, implying that sparrows do not adjust investment in response to parasitism risk. Pre-laying ambient temperature and precipitation were not associated with egg size, yet females tended to lay more eggs under rainier conditions. Overall, we provide evidence that both endogenous and exogenous factors shape female reproductive investment. Understanding the flexibility of reproductive strategies in response to multiple sources of selection, and how this mediates key trade-offs that influence demographic rates, can be used in forecasting population growth of bird species affected by anthropogenic changes to breeding areas.

Over the past four decades, rising temperatures have impacted the breeding phenology of many bird species, in some cases with consequences for their reproductive success. Migratory birds face particular challenges in shifting breeding phenology to track warmer springs, and understanding the impacts of rising spring temperatures on migratory birds' breeding is urgent. Here, we use over 4000 UK observations of Common Redstart nests, and spring temperature data from 1974 to 2020, to examine the effect of spring temperatures on laying date, clutch size and brood size. We use a sliding window approach to detect periods over which traits are most sensitive to temperature, and compare phenotypic responses to temperature over space and time with the aim of identifying causal effects of temperature and inferring the contributions of plasticity and local adaptation. We found that redstart laying date was sensitive to spring temperature from mid-April to late May, with a relatively shallow response of 1–2 days/°C that was similar across space and time, but shallower than the phenological response of many of the resource species. Over the study period, laying date has advanced by more than 11 days, which is substantially more than can be explained based on the temperature plasticity estimates we obtained. Spring temperature had a weak, but positive, impact on clutch size, but with no evidence of an effect of spatial variation in temperature. The rate of brood size reduction from hatching to fledging became more negative at higher temperatures, but after taking into account a non-significant but positive effect of temperature on brood size at hatching, there was no net effect of temperature on fledging success. Taken together, we found little evidence that higher temperatures in the UK lead to lower reproductive output.

In the current biodiversity crisis, conservation efforts are often focused on extinction prevention. However, it can be difficult to determine if a species is extinct, especially if the species has an extensive range, including being a transcontinental migrant, or is poorly known. The breeding range of the migratory Critically Endangered Slender-billed Curlew Numenius tenuirostris is uncertain, and the species has an extensive non-breeding range that spans central Asia, eastern Europe, the Middle East, the Mediterranean basin and the northwest African coast. There have been no incontrovertible sightings since 1995. In this time, extensive and intensive searches for the species have continued. Using an IUCN extinction probability framework, we incorporate potential threats to the species, search effort and past records (museum specimens and confirmed and unconfirmed sightings, all of which are primarily from its non-breeding range) to assess the probability of extinction. The model indicates that there is a 96.0% probability that Slender-billed Curlew is no longer extant, classing it as Extinct according to IUCN Red List guidelines. Posterior probability Bayesian extinction date estimation modelling suggests an extinction year around the time of the 1995 sighting. Although several threats to the species have been suggested, those that definitively drove the species to extinction will never be known. Other species of Numenius are under a range of pressures, and many are recognized as globally threatened. To ensure the continued survival of all shorebird species, we advocate flyway-scale concerted, coordinated action, and caution against complacency even for widespread but threatened taxa in Europe.

Sexual traits, such as visual adornments, sound-based cues and courtship dances, are frequently displayed in combination as multimodal signals. Some hypotheses propose that different signals trade-off with each other, potentially due to resource limitations (‘trade-off’ or transfer hypothesis) or that these develop simultaneously to enhance communication effectiveness (‘joint evolution’ hypothesis). Alternatively, multiple cues may evolve independently to serve distinct functions or convey different information (‘multiple messages’ hypothesis). Here, we explored the interdependence between different signal modalities in manakins (Pipridae), which are known for great interspecific diversity in the degree of elaboration in courtship dance, song and plumage coloration. We also used comparative methods to explore the mode of evolution and the degree of conservatism of these signals. We found that song, plumage coloration and courtship dance evolved independently as there was no correlation between these traits. Song evolution in manakins was attracted to a single optimum and exhibited a weak phylogenetic signal in comparison with those of colour and behavioural diversity. The high support found for the speciational and κ models when analysing the multivariate estimates of trait variability suggests that these signals (especially colour and behaviour attributes) may have evolved in a punctuated manner, with large evolutionary changes at speciation events and minimal subsequent changes along the branches. Our results show that song, colour and dance diversity are each associated (or marginally associated) with different ecological factors, indicating that sexual signals in manakins might convey different information and/or respond to different selection pressures. Larger species and those with lower dispersal capacity tend to exhibit higher colour richness, which in turn differed among lek categories, being higher in species with ‘classic’ leks and lower in non-lekking species. Overall, the present study supports the idea that correlation between signal modalities does not constitute a widespread pattern in songbirds.