Journal of Ornithology最新文献

The red-crested cardinal (Paroaria coronata) is an emblematic bird of the southern cone of South America that has been traditionally classified as sexually monomorphic and monochromatic from a human visual perspective. Using reflectance spectrometry, we analyzed sexual differences in the coloration of the red head plumage patch of adult wild red-crested cardinals in central-eastern Argentina. We also described sexual differences in body size and determined the onset of morphometric differences by comparing morphological measurements and growth rate between male and female nestlings. Adult males had on average longer wings and brighter red plumage relative to females. Similar to adults, nestlings were sexually dimorphic at fledging and presented sex-specific growth curves. Male nestlings grew faster and reached a larger size at the fledging time. Both for adults and nestlings, wing length was the trait that expressed sexual differences in body size. Our results are consistent with recent studies in passerines indicating that many birds considered sexually monochromatic are likely dichromatic when considering avian visual capacities. This study allows the red-crested cardinal to be re-categorized as sexually dimorphic and dichromatic.

South India’s Western Ghats are a global biodiversity hotspot and an area of conservation concern with numerous endemic species. There is an urgent need for accurate threat assessments for these species, including the Nilgiri Pipit (Anthus nilghiriensis). The Nilgiri pipit is endemic to the montane grasslands of the Western Ghats, and has experienced recent rapid habitat declines. Here, we characterize the climatic niche of this species using environmental niche modelling, and use these models to estimate its range and threat status. Using the Maxent modelling algorithm and presence data from surveys by expert observers, we find that the Nilgiri Pipit is strongly sensitive to higher temperatures. We project the best-performing models to the last glacial maximum and find evidence that the species had a considerably larger range under that climatic regime. We estimate that the extent of suitable available habitat is no more than 436 km² even using the most conservative threshold. Based on this result, and the documented decline in and fragmentation of its habitat, we recommend that the species be uplisted to “endangered” on the IUCN Red List, from its current status of “vulnerable”. Finally, we compare these results to models based on identically processed eBird data, and find that eBird data produce larger estimates of suitable habitat: we, therefore, recommend caution in the interpretation of environmental niche models based on eBird data.

Although the evolutionary ecology of melanin pigments and melanin-based coloration has been studied in great details, particularly in birds, little is known about the function of melanin stored inside the body. In the barn owl Tyto alba, in which individuals vary in the degree of reddish pheomelanin-based coloration and in the size of black eumelanic feather spots, we measured the concentration in melanin pigments in seven organs. The eyes had by far the most melanin then the skin, pectoral muscle, heart, liver, trachea, and uropygial gland. The concentration in eumelanin was not necessarily correlated with the concentration in pheomelanin suggesting that their production can be regulated independently from each other. Redder barn owls had more pheomelanin in the skin and uropygial gland than white owls, while owls displaying larger black feather spots had more eumelanin in the skin than small-spotted owls. More data are required to evaluate whether melanin-based traits can evolve as an indirect response to selection exerted on melanin deposition in organs.

Birds often have a peak of singing activity at dawn, and the timing of dawn song is species-specific. However, the start of singing at dawn may also depend on environmental factors. We investigated the effects of different environmental variables on the start of dawn singing in six common songbird species in the woodlands of the Swiss National Park. Moon phase, aspect, temperature and road noise had the most consistent effects across species: dawn singing started earlier after brighter and warmer nights, on more east-exposed slopes, and in areas with more road noise. On average, birds started to sing 2.8 min earlier in areas with high road noise level compared to areas without road noise, and 4.7 min earlier in east-exposed slopes compared to west-exposed slopes. Further, birds started to sing on average 5.0 min earlier after full moon compared to new moon nights, 1.2 min earlier after warmer compared to colder nights, and 2.5 min earlier at 2200 m than at 1500 m a.s.l. The effects of date were more species-specific: Alpine Tits started to sing on average 4.9 min later at the end compared to the beginning of the study period, whilst Song Thrushes started to sing 9.0 min earlier. Our findings are in line with the results of previous studies on the effects of road noise, nocturnal light, and partly on temperature. Our study shows that variation in environmental variables may influence the start of dawn singing in different ways, and that anthropogenic factors like road noise can affect bird behaviour even in a highly protected area.

Conditions encountered during early development affect future survival and reproduction in many bird species. For parents, it is important what body condition the nestlings will achieve at fledging because the condition affects the offspring’s chances to survive and reproduce in the future. However, there is a trade-off between the number of nestlings and their condition. We studied parental behaviour and nestling body condition in uniparental Penduline Tits. In this small passerine, the parental care (incubation and food provisioning) is provided by the female only (49% of clutches in the study population) or the male only (15%). In addition, over a third of clutches are deserted by both parents before the start of incubation. We found that female-only cared clutches had more eggs and nestlings and produced more fledglings than male-only cared clutches. The incubation behaviour and incubation temperature in both types of clutches were similar. The provisioning rate per brood was positively, and the provisioning rate per nestling was negatively, correlated with brood size. Although males cared for smaller clutches, parent sex was not significant in both models of provisioning rates (per brood and per nestling). Moreover, the provisioning rate did not predict the brood’s average nestling condition. However, nestlings reared in broods with male care were in better condition than those reared by females. At the age of 13 days, they had a higher scaled mass index (describes the relative size of energy reserves) and higher haemoglobin levels. The results suggest that the lower productivity of male-only cared clutches, compared to those cared for only by females, may be compensated by the higher condition of nestlings. Information about the recruitment success of broods cared for by males and females will be necessary to test this prediction.

Social learning is an important aspect of dealing with the complexity of life. The transmission of information via the observation of other individuals is a cost-effective way of acquiring information. It is widespread within the animal kingdom but may differ strongly in the social learning mechanisms applied by the divergent species. Here we tested eighteen Kea (Nestor notabilis) parrots on their propensity to socially learn, and imitate, a demonstrated sequence of steps necessary to open an apparatus containing food. The demonstration by a conspecific led to more successful openings by observer birds, than control birds without a demonstration. However, all successful individuals showed great variation in their response topography and abandoned faithfully copying the task in favour of exploration. While the results provide little evidence for motor imitation they do provide further evidence for kea’s propensity towards exploration and rapidly shifting solving strategies, indicative of behavioural flexibility.

Improving our understanding of the spatio-temporal distribution of migratory game species is pivotal for developing flyway-based management strategies. We used miniaturized GPS-Argos transmitters to analyse movement patterns, home-range, habitat use, and pre-breeding migratory dynamics of a medium-sized (~ 80 g) migratory songbird, the Fieldfare (Turdus pilaris). We focused on the population wintering in northern Italy, an area where this species is subject to intense hunting pressure during autumn–winter. Most individuals were relatively sedentary upon reaching their wintering area, with only a few performing erratic movements up to mid-January. Forest and farmland were the most used habitats during both early and late winter. We obtained partial information on pre-breeding migration from 16 individuals. Pre-breeding migration began on 21 March on average (min.: 7 March, max.: 7 April). We identified north-western Russia (longitudes 35–50° E) as the putative breeding area of six individuals, while a single individual migrated to Finland. Our novel individual-based tracking study of south-European wintering Fieldfares thus highlights that Russia, rather than Scandinavia, is likely the main origin area for Italian wintering birds, improving previous knowledge based on recoveries of ringed birds. Our findings suggest that an effective flyway-based management plan for a sustainable exploitation of the Fieldfare in southern Europe may be hindered by knowledge gaps on the conservation status of this species over its broad breeding range, which extends to distant Russian regions.

Understanding the mechanisms and the factors influencing the phenology, reproduction and biometrics of long-distance migrants are extremely important as global climate warming has induced changes in the locations of geographic ranges and dates of migration and reproduction. In this article, we compare phenology, reproductive parameters and adult biometrics of core and peripheral populations of a rare and endangered bird—the barred warbler Curruca nisoria—that inhabits the farming landscapes and makes long-distance trans-continental migrations. We predicted that: (i) individuals nesting in the core population would be larger than in the peripheral population; (ii) the reproductive parameters of the Barred Warblers in the core population would be higher than in the peripheral population. The Barred Warblers nesting in the centre of the range laid larger clutches and were clearly larger than individuals from the small, peripheral population. However, no differences in egg size and productivity were observed between the analysed populations. The Barred Warblers synchronised their breeding dates over a large geographical area as they had only a short time window for reproduction and had to lay their eggs as soon as possible. Individuals arriving earlier on the breeding grounds had larger clutches, longer wings and produced more nestlings. The pressure of the passage of time during the breeding season was a more important factor than the geographical location affecting the breeding characteristics in these populations.

Mountain habitats harbour significant breeding populations of alpine bird species, yet they can also be important from a biodiversity conservation point of view outside the breeding season. High-elevations are likely important fuelling habitats for birds during the post-breeding period due to seasonal peaks in arthropod abundance being later relative to lowlands. There is no detailed study of bird communities using high-elevations in the post-breeding migration period in Europe. In this study, we recorded birds on line transects from August to October in 2021 and 2022 across an elevational gradient in the Western Italian Alps to assess how the abundance and diversity of birds varied in time and space during the autumn migration period. We detected 104 species in total, representing 22% of the Italian list of terrestrial bird species, showing that a wide range of bird species exploit these habitats. The highest bird diversity and abundance were found during the early migration period at the end of August when long-distance migrants use high elevations. Treeline habitats and south-facing slopes held the highest abundance of migrants, probably due to the high structural diversity and relatively high solar radiation which might affect thermoregulation and prey activity. We suggest that future management of protected areas in the mountains should take these parameters into account in order to protect mountain bird diversity, not only during the breeding season, but also in other key periods of the annual cycle, such as post-breeding migration. It is also essential to counteract the effects of climate and land-use change in mountain habitats by promoting conservation strategies for Alpine biodiversity, including migrants, over the entire year.

Habitat conditions surrounding individual birds are key components determining their fitness, notably by influencing effective foraging, escape from predators, and adaptation to changing environmental conditions. Birds living in dynamic habitats are particularly likely to have a high need to explore; however, spatial and temporal patterns of exploratory movements are poorly understood. We investigated the exploratory movements of adult common shelducks (hereafter Shelducks, Tadorna tadorna) in the Wadden Sea, which provides a dynamic habitat for birds. We captured nine shelducks in adjacent breeding areas and attached GPS satellite telemetry devices for 5–18 months, mostly covering the post-breeding period. We analyzed bird-movement patterns based on mean daily locations and behavioral change point analysis. All individuals explored on a median of 22% of tracking days (range = 6–39%). Individuals usually explored new areas for a short time before switching to stay in these areas for longer periods. Exploratory movements were particularly frequent before the start of the flightless period during molting. During this time, shelducks explored the traditional molting area in the Elbe estuary intensively. However, birds did not explore places within the area subsequently used for molting for longer or more often than other places. The molting area was used for a median of 59 days, i.e., about twice as long as required for the flightless period, suggesting that this area was explored not only to select a suitable molting place, but also for other purposes. Only two shelducks performed longer-distance exploration movements, i.e., > 45 km from their sedentary areas. We therefore concluded that exploratory movements by adult shelducks may enable the birds to adapt to small-scale changes in habitat conditions.