Journal of Ornithology最新文献

How the migration behavior of long-lived birds develops throughout their life is still a research question in ornithology that is largely unanswered. Here, we analyzed GPS data of 70 juvenile Black Storks during the first 3 years of their migration to determine the influence of age and experience on migration patterns. We focused on the choice of the migration flyway, as well as the movements in the wintering area, and the changes in departure times with increasing age. Migratory routes of German Black Storks were divided into the western (82% of all tracked individuals) and eastern flyways (16%). The central migratory flyway through Italy or Greece was taken only by two individuals and never repeatedly. In addition, we found that the wintering area decreased by almost 60% during their first 3 years of life. In addition, spring departure dates from the wintering areas also became earlier with increasing age. However, we did not find changes in departures from the breeding area in autumn. Thus, our study shows that age and migration experiences have a considerable influence on essential migratory decisions in Black Storks. Further, it also demonstrates that older storks rely strongly on previous experiences to perform their migrations efficiently.

The effectiveness of surveys of breeding birds varies due to multiple factors, with the primary being imperfect detection, which is particularly severe for elusive species. For example, the territory mapping method requires surveying an area multiple times a season to compensate for missing individuals during single surveys. Novel methods require much less effort in the field and include estimation of both detection probability and abundance corrected for individuals that went undetected. The aim of this study was to check if point counts and model-based results provide estimates similar to the ones from the territory mapping method. We studied the abundance of two forest birds—Goldcrest Regulus regulus and Firecrest R. ignicapilla—on three permanent census plots in the Białowieża Forest (E Poland). We compared abundance estimates resulting from the territory mapping method in its ‘standard’ (~ 10 visits) and intensive (~ 20 visits) approaches. We also performed point counts at the same plots using distance sampling methodology and hierarchical models in an attempt to get unbiased estimates by correcting for imperfect detection. We found that the standard territory mapping method produces much lower abundances than model-based estimates, which was particularly evident for the more numerous Firecrest. At the same time, results from point counts were more consistent with numbers from the intensive territory mapping. Our findings suggest that applying point counts and distance sampling models meet modern standards by considering various effects in abundance, availability and detection processes along with providing uncertainty of their estimates. We assume that our results might be applicable to other elusive species.

Abstract

Despite a clear preference of the Eurasian Three-toed Woodpecker Picoides tridactylus for spruce trees as foraging sites by both males and females, some studies showed intersexual resource partitioning that allows competition for food to be minimized. The objective of the study was to characterize foraging sites of the Three-toed Woodpecker in the primeval stands of the Białowieża National Park (BNP, Poland) in relation to sex. Although the woodpeckers foraged on seven tree species, both males and females foraged predominantly on spruce (83% and 90% of the observations, respectively). Selection indices showed a significant preference for dead spruce trees for both sexes and additionally for live spruce trees in the case of females. Spruce trees where woodpeckers foraged were twice as thick as those available, regardless of whether they were dead or alive. The only feature differentiating the feeding sites of males and females was the diameter of the part of the tree at foraging locations. This suggests that there is some niche partitioning between the sexes of the Three-toed Woodpecker in primeval stands of the BNP. Our research clearly showed that even in the very rich environment of the BNP, abounding in various forms of dead wood, large dead spruce trees are crucial for the Eurasian Three-toed Woodpecker.

Narrower habitat niche at the range margin may reduce the ability of specialized species to adapt to the changing environments and to shift the range. In most of its European range, the Crested Tit (Lophophanes cristatus) inhabits pine forests throughout the year; those forests are important timber production areas for forest industries. We studied the breeding distribution of this species in relation to forest characteristics in (i) the central part of the range in Estonia, where pine areas have undergone large transformations because of peatland drainage for forestry, and (ii) in isolated populations at the southern range margin in East Ukraine, where historical pine forest losses have been substituted with replanting. In Estonia, both the range of forest site types available and occupied by the species was wider than in Ukraine; the birds occupied forests starting from a younger age and reached higher population densities. A preference for natural mature pine stands was found only in the most peripheral and isolated populations in Ukraine. Larger areas of pine forests in Estonia and their higher historical connectivity may be an important factor that has allowed (large) local populations to adapt to the extensive recent transformations in these ecosystems. In contrast, the historical bottlenecks and isolation of suitable forest patches still limit the population in eastern Ukraine, and climatic, economic, and war-related pressures to pine forests are likely to expose these marginal populations to new fluctuations.

Differences in migratory behavior have been suggested to drive speciation, but the genetics underlying this process remain unknown. Identification and study of migratory divides can help us understand how differential migration can lead to reproductive isolation. Here, we genotyped Willow Warblers Phylloscopus trochilus, from the Åland islands, located in between the ranges of the differentially migrating subspecies P. t. trochilus and P. t. acredula. We found that Willow Warblers on the Åland islands were genetically intermediate to allopatric populations of both parental subspecies, providing evidence that the islands constitute a previously unknown hybrid swarm, likely to be a migratory divide. 

European Robins are well known for defending a winter territory. Both resident birds and newly arrived migrants defend a winter territory. However, little is known about the timing and drivers of the settlement of the winter territory in autumn. We hypothesized that settlement is triggered by the arrival of migratory Robins from the North. The hypothesis was tested by relating observational data on first autumn song (as indicator for the settlement of a winter territory) of European Robins in a back yard in the North of the Netherlands to nationwide arrival dates of migratory European Robins in the Netherlands. Date of first autumn song in the studied yard advanced significantly with 14 days from 1993 to 2021, but there was no significant relationship with nationwide autumn arrival dates. We conclude that first autumn song (as indicator of settlement of winter territory) in European Robin does not seem to be triggered by the arrival of (conspecific) migrants. We suggest instead that advanced timing of breeding caused the advancement of winter territory settlement. Climate change may allow resident Robins to moult earlier and settle before conspecific migrants arrive. However, this suggestion needs further testing.

Abstract

The mortality rate of long-distance migrants is known to peak in the period between fledging and completing the first year of life. Our understanding of this sensitive life stage, however, lags behind our understanding of determinants of nestling success (at least for temperate breeding birds). Here we collect diverse data (morphometrics, phenology, nest videos, radio tracking detections) on two generations of a long-distance migrant (the Purple Martin, Progne subis). We examine multiple life stages, to understand how in-nest conditions may carry over to the post-fledge period. Our data show that an earlier first-egg date is associated with higher parental quality as determined by their tracked movements and provisioning effort. Despite high variability in first-egg date, the duration of the nestling phase was approximately consistent between nests, with fledge-date and date of fledgling departure from the breeding grounds highly constrained by a relatively fixed duration of nestling development. Offspring of early-nesting parents fledged in better body condition, as evidenced by their larger wing chord measurements. Given the fixed nesting duration, this higher parental quality in early nesters led to early-season nestlings having the dual advantage of elevated body condition and early departure dates—two known predictors of first migration survival in this species and many others. Our work illustrates a potential carry-over effect from the nestling phase to fall-migration, and provides a useful example of linking diverse data sets across multiple life stages to extend our knowledge of breeding success to the less-understood post-breeding phase.

Monitoring of breeding success in wildlife is key for evaluating population trends and support conservation measures. However, it is challenging depending on breeding places or non-accessible habitat. In recent years, new technologies were applied to studies of bird biology, i.e. drones. UAV (drones) are available to study new aspects of bird ecology, which are not available using traditional methods. The Raven Corvus corax predominantly nests in upper tree canopies or on high cliffs. Hence, it is challenging to monitor it breeding success from the ground. Our study were conducted in forests in NE Poland, on the 77 arboreal Raven nests in 2021–2022. By using drones, we investigated (i) whether the classic data on breeding success from ground observations differ from those of nest inspections via drone, and (ii) to what extent the adult birds behave when the drone is used at the nest. The inspection from the ground failed to determine the contents of as many as 30% of the occupied nests. Inspections using a drone and those made from the ground yielded different results, as aerial assessment showed a higher number of the young (respectively 1.93 vs. 3.22 per successful brood). Broods with three young accounted for 6.5% of nests controlled from the ground and 23.3% using a drone, while broods with two young accounted for 33.8% and 10.4% of nests, respectively. During most of the inspected nests (65% of the cases), adult birds sat nearby in the tree tops and called. In 12% of the cases, the birds flew close to the nest, passing the drone at a distance of more than 20 m, and did not attempt to approach the device. In four cases, adult birds closed the drone at less than 10 m. A direct collision did not happen. The most vital reactions were recorded in several instances (only 4.2%) in which the birds were not near the nest when the inspection began but arrived during the inspection. Drone surveys have revealed previously un-described behavior of birds, alarmed at the examination of empty nests. In 50 nests, 65% of the cases, the Raven tolerated the drone’s presence at the nest, although the birds showed concern and occasionally defensive reactions. It seems that the adverse reaction of birds is weaker when they associate the appearance of a drone with human presence. Key recommendations: control in teams of two - operator and observer, starting end landing in close vicinity of the nest tree, immediate interruption of flight if birds react, forbade flying directly over the nest. It is advisable to check the reaction of adult Ravens to drone inspections of nests with small nestlings. To sum up, our study showed that the drone inspections did not harm the adult birds but provides a more reliable data for reproduction than the observation from ground.

Little is known regarding the migration routes of Siberian songbird populations. Here we provide the first geolocator tracking data for an Arctic Warbler breeding in Central Siberia and compare its movements with eight long-distance ring recoveries of this species. In autumn, the tracked individual migrated eastward to a stopover site in eastern Siberia, before migrating southward through Taiwan to its non-breeding sites in the Philippines and Indonesia. During spring migration, the bird spent at least one month at stopover sites in Mongolia, before migrating to its breeding site in June. Ring recovery data confirmed the movement between the Central Siberian breeding grounds and stopover sites in northern Mongolia.

Immune function shows intraspecific variation, with diet being a crucial factor that could explain such variation. Using the isotopic signature δ¹⁵N and C:N ratio, we evaluated the relationship between immune state (hemolysis and hemagglutination score) and natural variation in resource use in individuals of the species Diuca diuca. We found that some components of the immune state, specifically the hemagglutination score, correlated positively and significantly with the incorporation of animal material (high levels of δ¹⁵N), while the hemolysis score correlated positively with the C:N ratio. In this sense, we conclude that individuals of Diuca Finches that fed with a variety of prey exhibit a better immune state.