Ibis最新文献

Insectivorous bird populations are declining globally, as are the insects upon which they depend. Furthermore, many of the plants on which those herbivorous insects depend are being displaced by the spread of agriculture and invasion by exotic species. We discuss the consequences of these declines for changes in trophic control of herbivorous insects by insectivorous birds, and the indirect effects on host plants. We first briefly review the evidence for and causes of bird and insect decline, and the current evidence for trophic control by insectivorous birds. We then hypothesize how trophic control may change under three scenarios: reduced bird populations alone, invasion by exotic insect species and conversion of native habitat to agriculture. We hypothesize that trophic control will decrease under all three scenarios, resulting in higher abundance of herbivorous insects and more frequent outbreaks, higher chronic levels of herbivory and reduced primary productivity. Because birds often specialize to some degree on certain insect species and forage preferentially in certain plant species, reduced trophic control may in turn reduce plant diversity in more native vegetation. Similarly, reduced trophic control in agriculture will require greater reliance on pesticides and, with it, the negative consequences of increased pesticide use.

Extensive research has focused on effects of non-breeding helpers on the reproductive success of cooperatively breeding birds, yet in the cooperatively breeding Florida Scrub Jay Aphelocoma coerulescens about half of breeding pairs do not have helpers in any given year. We tested for effects of breeder experience and environmental variables (acorn abundance, fire history and territory size) on reproductive output of breeding pairs that lacked helpers. In generalized linear mixed models, explanatory variables that best explained variation in reproductive output included female breeder experience, time since fire, territory size and acorn crop. Our results emphasize that active habitat management through prescribed fire enhances the reproductive success of this declining bird across a diversity of social group compositions.

Greenland White-fronted Geese Anser albifrons flavirostris exhibit prolonged parent–offspring and sibling–sibling associations, suggesting fitness advantages to such behaviour, so we used reduced representation genome sequence data to determine the degree to which marked flock members observed associating in apparent parent–offspring and sibling–sibling relationships in the field were genetically related. Among 50 bled, marked and released geese, we genetically identified members of 11 different family groups, confirming all observed male parent–offspring relationships as genetically predicted, but only 10 out of 12 (83%) possible female parent–offspring relationships (i.e. two offspring were not genetically related to the adult female in their family groups observed in the field); these two ‘adopted’ offspring were responsible for four (15%) of the cases where observed ‘siblings’ were not genetically related to other family-member first-winter birds with which they associated. One multigenerational family consisted of three genetically confirmed grandmother–mother–sibling offspring relationships, not previously reported in arctic-nesting geese, as well as one of the two ‘adopted’ first-winter geese.

Anthropogenic noise is considered one of the most serious forms of pollution globally and has been shown to have negative effects on the distribution, behaviour, cognition and reproductive success of animal species worldwide. Among the most commonly reported impacts of anthropogenic noise are its effects on acoustic communication. Animals may adjust the rate, amplitude, duration and/or frequency of their acoustic signals to better maintain communication when anthropogenic noise is present. One of the most commonly reported vocal adjustments in noisy conditions, an increase in amplitude known as the Lombard effect, has been reported in almost all animal species tested to date. In this study, we combine behavioural focals and amplitude measurements to investigate whether female Western Australian Magpies Gymnorhina tibicen dorsalis alter the rate and amplitude of their territorial song (known as a carol) when unmanipulated levels of anthropogenic noise are present. Magpies reduced the rate at which they carolled when loud anthropogenic noise (>50 dB) was present but, contrary to our prediction, we found no evidence that magpies adjusted the amplitude of their carols under these conditions. Reduced carolling rates during anthropogenic noise may minimize the energetic expense associated with vocalizing when it is likely that such vocalizations will be masked by anthropogenic noise. However, a reduction in carolling rate may negatively affect the sociality and territoriality of magpies, as carols are important for these aspects of life. Our study adds to the growing body of literature documenting changes to the vocal behaviour of wildlife in the presence of anthropogenic noise.

Fine-scale spatial and temporal genetic structuring of nests is possible in colonial birds that return to breed at their natal sites, and notably in waterfowl for which females are more philopatric than males. We genotyped female Red-breasted Mergansers Mergus serrator breeding colonially on a coastal archipelago in eastern New Brunswick, Canada, during 2015 and calculated pairwise kinship coefficients using 4270 single nucleotide polymorphisms to assess whether related hens nest near each other and initiate their nests around the same time. We found no spatial or temporal genetic structure across islands; however, nesting was relatively synchronous between hens nesting close together. Red-breasted Mergansers initiating their nests at the same time may select nearby nest-sites based on the availability of dense vegetation that conceals nests, limiting opportunities for kin to nest near one another in this population.

The European Turtle-dove Streptopelia turtur is globally threatened, with populations experiencing substantial declines in recent years. On the breeding grounds, the habitat associations and main causes of decline have been identified, but little is known about the species across its Sahelian non-breeding (wintering) areas. To identify environmental correlates of its wintering distribution, a priority action in the International Species Action Plan, we fitted 42 birds with satellite devices on the breeding grounds in France and the UK between 2012 and 2016. We related the best accuracy class locations of those 14 birds reaching the wintering grounds to environmental data derived from satellite remote sensing at a landscape scale and core areas scale. The tagged birds spent the winters in Senegal, The Gambia, Mali and Mauritania. Eleven showed a distinct southward shift in home-range between early and late winter, moving from areas with low rainfall the preceding summer (< 600 mm) to areas with higher summer rainfall and which had a broader range of normalized difference vegetation index values. In both time periods and at both landscape and core areas scales, birds were consistently associated with proximity to water sources in a mixed landscape of open forests, shrubs, natural grasslands and croplands: a typical mix of habitats in the Sahelian and Sudanian-Sahelian seasonally flooded basins with riparian forests of Acacia nilotica. These persistent habitat associations throughout the winter are likely to reflect individuals tracking resources required for food, water, and places to roost and shelter. Increasing human-related pressure on this landscape may well be reducing the extent of available habitat and could be a contributory factor in the decline of this species. Conservation and regeneration of riparian forests and floodplains could offer significant benefits to biodiversity and potentially contribute to the livelihoods and well-being of local communities.

Climate change is driving phenological shifts in migration and reproduction, yet it remains unclear how moult, the stage through which birds replace degraded feathers, is affected. Moult is a constitutive element of self-maintenance and survival and therefore investigating shifts in moult is pivotal for advancing our understanding of avian responses to climate change. Drawing on life-history theory, we proposed four non-mutually exclusive hypotheses to explain pre-basic moult phenology in a Mediterranean climate with a prolonged drought period. Specifically, we hypothesized that birds advanced their primary feather moult in response to (1) increased temperature, (2) decreased precipitation, with (3) the strongest effects of temperature in the driest years, and (4) an inverse relationship between moult start date and duration. We also investigated whether the median brood patch date (as a metric of breeding phenology) was a strong predictor of moult start date. We leverage 16 years of data for two passerine species and used Zucchini–Underhill models with multiple regressions to elucidate these patterns. Bushtits Psaltriparus minimus had a 27-day advancement in moult start date in the hottest years compared with the coolest, and had an inverse relationship between moult start date and duration. Song Sparrows Melospiza melodia had an 18-day advancement in the driest years compared with the wettest. We did not find any interaction effects between temperature and precipitation on moult. Finally, median brood patch date was not a significant predictor of the annual variability in primary moult start date for either species. The observed plasticity in moult phenology suggests long-term advancement of pre-basic moult timing for Bushtits and increased stochasticity for Song Sparrows as climate change intensifies. Our results demonstrate that moult phenology, similar to migration and reproduction, responds to changes in environmental conditions.

The vocalizations of male Cuculus cuckoos exhibit clear interspecific differentiation, whereas female vocalizations, characterized by the distinctive bubbling calls, exhibit a high degree of similarity across species. Although structural differences in female bubbling calls among Cuculus cuckoos have been reported, their functional role and practical use by males for species delimitation have rarely been established. In this study, we conducted playback experiments with manipulated female calls to identify call parameters that elicit male responses in Common Cuckoos Cuculus canorus. To this end, we modified three parameters (number of notes, delta time and highest frequency) of female calls recorded in the field and recorded the response of males to these alterations. We found that male cuckoos exhibited varying approach rates in response to subtle changes in female calls, with responses differing according to the specific parameters: a linear relationship for the number of notes and non-linear relationships for others. Among these parameters, the highest frequency of the bubbling call appeared to be the primary criterion for delineating species boundaries. However, the overall results suggested that multiple parameters of the bubbling call, rather than a single feature, collectively contribute to species delimitation in Common Cuckoos. Further playback studies incorporating multiple manipulations of bubbling calls simultaneously would provide deeper insights into the evolution and functional significance of female calls in cuckoos.

With the death of Mike Harris on 17 December 2023, at the age of 84, the world lost one of its best known, most loved and most outstanding seabird biologists. For no less than 63 years, Mike studied seabirds, and was active in the field and publishing into his last year. Research Gate lists him as having 332 publications in total and 15 927 citations, including his many collaborative studies.

As for his early life, Michael Philip Harris was born in Swansea on the Welsh coast on 28 April 1939. The son of a motor mechanic, he attended local schools and also studied at Swansea University for BSc and PhD degrees. His passions for natural history, marine life and islands were evident from an early age, with much of his boyhood spent exploring the local countryside, and developing the field-craft that served him well through later life. He was inspired by the writings of fellow Welshman, Ronald Lockley, about the very islands and bird populations on which Mike would himself subsequently work. A brief spell acting as assistant warden at the Bird Observatory on Bardsey Island, off the north Welsh coast, helped to hone his skills in trapping, handling and ringing birds.

This was followed by PhD studies on Herring Gulls Larus argentatus and Lesser Black-backed Gulls L. fuscus on Skomer Island. In the summers of 1962 and 1963, this work entailed swapping all the eggs in several Lesser Black-backed Gull colonies with eggs in Herring Gull colonies to investigate aspects of species recognition and migration, forming one of the first large-scale field experiments in British ornithology (Harris 1970). After completing his PhD, his examiner, David Lack, offered Mike a position at the Edward Grey Institute in Oxford, spanning the period 1962–73. He began with studies of gulls, Oystercatchers Haematopus ostralegus and Manx Shearwaters Puffinus puffinus on Skokholm Island, which he combined with being warden of the Bird Observatory there, another link with Ronald Lockley. While still based at the EGI, Mike moved to the Galápogos Islands in the late 1960s to study the nesting ecology of tropical seabirds, notably storm petrels and albatrosses. He discovered that the population of Band-rumped Storm Petrels Hydrobates castro consisted of two sectors, one nesting in one half of the year, and the other nesting in the second half, but both using the same set of burrows (Harris 1969). Over the same period, Mike also produced the first Field Guide to the Birds of Galapagos (1974) still in use today. All this early work was undertaken at a time when fieldwork logistics, especially on remote islands, were much more challenging than today, with no computers, mobile phones or bird-borne data loggers.

While on Galápagos, Mike developed a friendship with Lars-Eric Lindblad who was interested in developing sustainable eco-tourism. He provided the funding which enabled Mike to develop the syste