Large-Scale Climatic Patterns Have Stronger Carry-Over Effects than Local Temperatures on Spring Phenology of Long-Distance Passerine Migrants between Europe and Africa

Earlier springs in temperate regions since the 1980s, attributed to climate change, are thought to influence the earlier arrival of long-distance migrant passerines. However, this migration was initiated weeks earlier in Africa, where the Southern Oscillation, Indian Ocean Dipole, North Atlantic Oscillation drive climatic variability, and may additionally influence the migrants. Multiple regressions investigated whether 15 indices of climate in Africa and Europe explained the variability in timing of arrival for seven trans-Saharan migrants. Our response variable was Annual Anomaly (AA), derived from standardized mistnetting from 1982–2021 at Bukowo, Polish Baltic Sea. For each species, the best models explained a considerable part of the annual variation in the timing of spring’s arrival by two to seven climate variables. For five species, the models included variables related to temperature or precipitation in the Sahel. Similarly, the models included variables related to the North Atlantic Oscillation (for four species), Indian Ocean Dipole (three), and Southern Oscillation (three). All included the Scandinavian Pattern in the previous summer. Our conclusion is that climate variables operating on long-distance migrants in the areas where they are present in the preceding year drive the phenological variation of spring migration. These results have implications for our understanding of carry-over effects

Sexual dimorphism in adult Little Stints (Calidris minuta) revealed by DNA sexing and discriminant analysis

Background The sex of an individual organism plays such an important role in its life cycle that researchers must know a bird’s sex to interpret key aspects of its biology. The sexes of dimorphic species can be easily distinguished, but sexing monomorphic bird species often requires expensive and time-consuming molecular methods. The Little Stint (Calidris minuta) is a numerous species, monomorphic in plumage but showing a small degree of reversed sexual size dimorphism. Females are larger than males but the ranges of their measurements overlap, making Little Stints difficult to sex in the field. Our aim was to develop reliable sexing criteria for Little Stints in different stages of primary moult during their stay on the non-breeding grounds in South Africa using DNA-sexed individuals and discriminant function analysis. Methods We caught 348 adult Little Stints in 2008–2016 on their non-breeding grounds at Barberspan Bird Sanctuary. To molecularly identify the birds’ sex we used P2/P8 primers and DNA isolated from blood samples collected in the field. We used Storer’s dimorphism index to assess the degree of sexual size dimorphism. Then we divided our sample into two groups: before or during and after primary moult. For each group we developed two functions: one using wing length only and the other a combination of morphometric features including wing, tarsus and total head length. Then we used a stepwise procedure to check which combination of measurements best discriminated sexes. To validate our result we used a jack-knife cross-validation procedure and Cohen-kappa statistics. Results All the morphometric features we measured were bigger in DNA-sexed females than in males. Birds with fresh primaries had on average 2.3 mm longer wings than those with worn primaries. A discriminant function using wing length (D1) correctly sexed 78.8% of individuals before moult, and a stepwise analysis showed that a combination of wing length and tarsus (D2) correctly identified the sex of 82.7% of these birds. For birds with freshly moulted primaries a function using wing length (D3) correctly classified 83.4% of the individuals, and a stepwise analysis revealed that wing and total head length (D4) classified 84.7%. Discussion Sexual size differences in Little Stints might be linked to their phylogenetics and breeding biology. Females are bigger, which increases their fecundity; males are smaller, which increases their manoeuverability during display flights and hence their mating success. Little Stints show an extreme lack of breeding site fidelity so we did not expect a geographical cline in their biometrics. Sexing criteria available for Little Stints in the literature were developed using museum specimens, which often shrink, leading to misclassification of live birds. The sexing criteria we developed can be used for studies on Little Stints at their non-breeding grounds and on past data, but should be applied cautiously because of the overlapping ranges

Contrasting strategies for wing‐moult and pre‐migratory fuelling in western and eastern populations of common whitethroat Sylvia communis

Trade‐offs between moult and fuelling in migrant birds vary with migration distance and the environmental conditions they encounter. We compared wing moult and fuelling at the northern and southern ends of migration in two populations of adult Common Whitethroats Sylvia communis. The western population moults most remiges at the breeding grounds in Europe (e.g. Poland) and migrates 4000–5000 km to western Africa (e.g. Nigeria). The eastern population moults all remiges at the non‐breeding grounds and migrates 7000–10 000 km from western Asia (e.g. southwestern Siberia) to eastern and southern Africa. We tested the hypotheses that: (1) Whitethroats moult their wing feathers slowly in South Africa, where they face fewer time constraints than in Poland, and (2) fuelling is slower when it coincides with moulting (Poland, South Africa) than when it occurs alone (Siberia, Nigeria). We estimated moult timing of primaries, secondaries and tertials from moult records of Polish and South African Whitethroats ringed in 1987–2017 and determined fuelling patterns from the body mass of Whitethroats ringed in all four regions. The western population moulted wing feathers in Poland over 55 days (2 July–26 August) at a varying rate, up to 13 feathers simultaneously, but fuelled slowly until departure in August–mid‐September. In Nigeria, during the drier period of mid‐February–March they fuelled slowly, but the fuelling rate increased three‐fold in April–May after the rains before mid‐April–May departure. The eastern population did not moult in Siberia but fuelled three times faster before mid‐July–early August departure than did the western birds moulting in Poland. In South Africa, the Whitethroats moulted over 57 days (2 January–28 February) at a constant rate of up to nine feathers simultaneously and fuelled slowly from mid‐December until mid‐April–May departure. These results suggest the two populations use contrasting strategies to capitalize on food supplies before departure from breeding and non‐breeding grounds.Appendix S1. Fig. S1. Moult timing and sequence of each wing feather for western (Poland–Nigeria) and eastern (Siberia–South Africa) Whitethroats. Fig. S2. The number of wing flight feathers growing simultaneously with the feather on the X‐axis for Common Whitethroats in Poland and in South Africa. Table S1. Mean relative mass of flight feathers in adult Common Whitethroats expressed as a percentage of the total mass of all wing feathers treated as 100%, and as percentage of the total mass of all primaries (P1–P9) treated as 100%. Table S2. Moult sequence and moult parameters of separate wing feathers for adult Common Whitethroats caught in July–October 2013–2016 in Poland. Table S3. Moult sequence and moult parameters of separate wing feathers for adult Common Whitethroats caught in November–April 1987–2017 in South Africa. Table S4. Underhill–Zucchini moult models used to determine the effect of region where moult takes place (see Fig. 1) on moult parameters estimated for all primaries, secondaries and tertials jointly in adult Common Whitethroats caught in July–October 2013–2016 in Poland and in November–April 1987–2017 in South Africa. Table S5. Mean wing lengths of Whitethroats caught in the four study regions (Fig. 1), considering the moult status of measured wings. Table S6. Comparison of primary moult rates estimated by Underhill–Zucchini models for Whitethroats in Poland and in South Africa (Tables S2 and S3) with those for other insectivorous passerine migrants.Appendix S2. Datasets used in the study.Polish ringing stations were supported by the Ministry of Higher Education (‘SPUB’ grants). This study was supported by a research grant from the National Research Foundation (NRF) of South Africa, and the National Centre for Research and Development (NCBR), Poland, within the Poland‐South Africa Agreement on Science and Technology (PL‐RPA/BEW/01/2016).http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1474-919X2020-10-01hj2019Oral Pathology and Oral Biolog

Biological Earth observation with animal sensors

Space-based tracking technology using low-cost miniature tags is now delivering data on fine-scale animal movement at near-global scale. Linked with remotely sensed environmental data, this offers a biological lens on habitat integrity and connectivity for conservation and human health; a global network of animal sentinels of environmen-tal change

Carry-Over Effects of Climate Variability at Breeding and Non-Breeding Grounds on Spring Migration in the European Wren <i>Troglodytes troglodytes</i> at the Baltic Coast

Many studies have linked changes in avian phenology in Europe to the North Atlantic Oscillation (NAO), which serves as a proxy for conditions in western Europe. However, the effects of climate variation in other regions of Europe on the phenology of short-distance migrants with large non-breeding grounds remain unclear. We determined the combined influence of large-scale climate indices, NAO, the Mediterranean Oscillation Index (MOI), and the Scandinavian Pattern (SCAND), during the preceding year on spring migration timing of European wren at the southern Baltic coast during 1982–2021. We modelled the effects of these climate variables on the entire passage and subsequent percentiles of the wren’s passage at Bukowo-Kopań and Hel ringing stations. Over 1982–2021, the start and median of migration shifted earlier at Hel, but the end of passage shifted later at both stations. In effect, the duration of passage at Hel was extended by 7.6 days. Early passage at Hel was related with high MOI in spring and the preceding autumn. Spring passage at Bukowo-Kopań was delayed after high NAO in the previous breeding season, and high winter and spring NAO. Late spring passage occurred at both stations following a high SCAND in the previous summer. At both locations, an early start or median of passage followed high local temperatures. We conclude that phenology of the wren’s spring migration at the Baltic coast was shaped by conditions encountered at wintering quarters in western Europe, where NAO operates, and in the south-eastern Europe, where the MOI operates, in conjunction with conditions in Scandinavia during the previous breeding season. We demonstrated that climate variability in various parts of the migrants’ range has combined carry-over effects on in migrants’ phenology in Europe

Sex and age differences in the development of breeding plumage in the Wood Sandpiper Tringa glareola during spring migration in north-eastern Poland

We investigated the effects of sex and age on the progression of breeding plumage moult in the Wood Sandpiper, a migrant wader that shows weak sexual size dimorphism and no dichromatism. We sexed the birds by DNA and examined the plumage of 416 Wood Sandpipers caught at a spring stopover site in north-eastern Poland. We scored the proportion of new breeding-type feathers on the head, back and scapulars in 20%-wide stages, and summed these scores as a body moult index, and on the lesser and median wing coverts summed as a wing covert moult index. Only 10% of all these birds fully developed breeding plumage on the upper body and 8% had only 21-40% of new feathers there. About 90% of the birds had moulted less than half of their wing coverts. No Wood Sandpiper showed a complete breeding plumage. We investigated whether moult indices were related to the date of the bird's capture and its body mass adjusted for size, age and sex, using generalised linear models. The best model indicated that the body-moult index was significantly affected by age, sex and year. Immatures had a more advanced body moult than adults, and females were more advanced than males. None of the predictors had a significant effect on the wing-covert moult index

Investigations of sexual dimorphism in live Kittlitz’s Plover Charadrius pecuarius from inland South Africa

Charadrius plovers generally show little sexual or seasonal dimorphism in size and coloration, but most published measurements come from museum specimens. We aimed to determine sexual size dimorphism in live Kittlitz’s Plovers Charadrius pecuarius, based on measurements of 96 males and 112 females ringed at Barberspan Bird Sanctuary (North West province, South Africa) between February 2008 and October 2009 and sexed by DNA analysis. The females were significantly heavier than the males in September–October, but their mass decreased significantly from September to the end of March (b = -0.10, t = 3.82, P = 0.0002), likely because of egg laying. Body mass has limited utility for sexing, because heavy birds with high fat scores of both sexes, possibly itinerants, occurred in all months. Tarsus-and-toe length differed between sexes (P = 0.066). Wing length of birds with old primaries decreased in September–October (ANCOVA, F1,153 = 8.84, P = 0.003), but did not differ between the sexes (ANCOVA, F1,153 = 0.23, P = 0.626). Wing length for birds with fresh feathers, total head length, bill length, tarsus length and height of the white forehead patch did not differ between sexes. We attribute this lack of any clear sexual dimorphism to the species’ monogamous mating system and shared parental care, and to its simple terrestrial displays, which would likely result in weak intersexual selection.OSTRICH 2011, 82(2): 135–13

The further the flight, the longer the wing: relationship between wing length and migratory distance in Old World reed and bush Warblers (Acrocephalidae and Locustellidae)

We analysed how body mass, migration distance, taxonomic family and breeding on small islands vs. continents affect wing length in 72 species of closely related Old World reed and bush warblers (Acrocephalidae and Locustellidae), based on literature data. The species we analysed share similar morphology, habitat, food preferences, feeding habits and breeding systems, but their migratory behaviour varies from sedentariness to long-distance migration. The mean wing length of these species was strongly correlated with their body mass, migration distance and taxonomic family (R 2 = 0.824; p = 3.2 26). The wing was on average 23.4% longer for each doubling of body mass and 2.7% longer for each 1,000 km of migration distance. Breeding on small islands was not significantly re-lated to wing length. Species of Acrocephalidae had on average 11.7% longer wings than Locustellidae with the same body mass and migration distance. The relationship between migration distance and standardised wing length was identical in both families (differ-ence between slope coefficients b: t-test: t = 0.19, p = 0.85). After we partly controlled for the effects of different habitats and behaviours, our results showed that at inter-specific level migration affects wing length in proportion to migration distance

Age-dependent differences in iris colouration of passerines during autumn migration in Central Europe

Avian eye colour changes with age, but many aspects of this transition are still insufficiently understood. We examined if an individual’s sex, age, species and body condition are related to the iris colour in common migratory passerines during their autumn passage through Central Europe. A total of 1,399 individuals from nine numerous species were ringed and examined in late autumn in northern Poland. Each individual was sexed by plumage (if possible) and assigned to one of three classes of the iris colour—typical for immatures, typical for adults and intermediate. We found that the iris was typical in 97.7% cases of immatures and in 75.8% cases of adults and this difference was significant. Species, sex and body mass index (BMI) had no significant influence on the iris colour. We show that iris colour in passerines in late autumn is strongly age-dependent and thus can serve as a reliable feature for ageing in field studies, especially in species difficult to age by plumage

Seasonal fluctuations in population size and habitat segregation of Kittlitz’s Plover Charadrius pecuarius at Barberspan Bird Sanctuary, North West province, South Africa

Seasonal fluctuations in population size reflect breeding patterns and movements of birds, but distinguishing residents from itinerant birds is difficult with partially migratory species such as Kittlitz&rsquo;s Plover. We determined changes in the size of Kittlitz&rsquo;s Plover populations in two microhabitats (Goose Point and Sandy Beach) at Barberspan Bird Sanctuary, North West province, South Africa, where we ringed waders between February 2008 and May 2010. Using a Bayesian model, we estimated the population of this species at these two sites from capture&ndash;recapture data gathered in eight 3- to 12-day collection periods. The estimated adult population at Goose Point peaked at 161 in October 2009, but decreased to about 40 in March 2009 and March 2010. The immature population peaked at 119 in January&ndash;February 2010. This, along with observations of nests and chicks, suggests that residents bred at Goose Point from September to March. The estimated number of adults at Sandy Beach increased from 48 in March 2010 to 380 in April 2010. Adults captured there in April 2010 formed feeding flocks and were heavier than the resident birds at Goose Point. These results suggest that Barberspan Bird Sanctuary supports resident and itinerant populations that are partially segregated in different microhabitats.OSTRICH 2011, 82(3): 207&ndash;21