Understanding migratory connectivity is fundamental to interpreting range dynamics and determining the drivers of population change. Stable hydrogen isotope ratios can be used to infer the provenance of individual migrants due to predictable broad‐scale spatial trends. We compare hydrogen isotopes (δ 2 H) among and within three Phylloscopus taxa occurring in Britain during post‐breeding migration to characterize patterns of connectivity. δ 2 H values of nominate Common Chiffchaffs Phylloscopus collybita were significantly higher than, and did not overlap with, those of Siberian Chiffchaffs P. c. tristis or Yellow‐browed Warblers P. inornatus . We found no evidence of a difference between the latter two taxa. There was a significant negative relationship between wing length and δ 2 H in the nominate Common Chiffchaffs. A negative but weakly supported trend between wing length and δ 2 H was also found in Yellow‐browed Warblers with no relationship found in Siberian Chiffchaffs. Our results suggest broad geographical structuring within nominate Common Chiffchaffs passing through Britain but weak evidence for this in Yellow‐browed Warblers and Siberian Chiffchaffs. The origins of Yellow‐browed Warblers and Siberian Chiffchaffs are probably largely overlapping and unlikely to be confined to the western range edge.
Owls (Strigiformes) and nightjars (Caprimulgiformes) play important ecological roles but remain among the least studied avian groups, with critical knowledge gaps potentially limiting effective conservation planning. We conducted a systematic literature review to quantify temporal, spatial, taxonomic and thematic patterns of research on African owls and nightjars. We also developed a Research and Conservation Priority Index (RCPI) that combines conservation concern and research scarcity, examined the relationship between threat status and research attention, and evaluated socio‐economic predictors of research effort. Research output increased substantially over the past five decades but remained geographically, taxonomically and thematically uneven, being concentrated in a small number of countries and widespread species. More than two‐thirds of species were under‐studied or had no published studies. Threat status was not associated with research scarcity, indicating that conservation concern and research attention represent distinct dimensions of species prioritization. The RCPI identified several threatened, range‐restricted and Data‐Deficient species, including the Annobon Scops Owl Otus feae , Itombwe Owl Tyto prigoginei and Maned Owl Jubula lettii , for which conservation concern coincides with limited scientific knowledge. Research effort was positively associated with the Human Development Index, suggesting that socio‐economic capacity influences knowledge production across African countries. These findings highlight persistent research biases and demonstrate the need to align future knowledge generation with conservation planning. Importantly, addressing knowledge gaps should complement, rather than replace, immediate conservation action for species facing known threats. Targeted investment in under‐represented regions, passive acoustic monitoring, citizen science and research on under‐studied threats will help strengthen evidence‐based conservation of Africa's owls and nightjars.
Mapping methods have played a crucial role in bird monitoring and for testing ecological hypotheses, theories and accuracy of other count techniques. The purpose of this review is to describe bird territory mapping methods, their development, principles, types and accuracy, and to compare their estimates with those of other quantitative methods. The mapping method was developed by a US ornithologist, A.B. Williams, in 1936. Since then, these methods have been used in large‐scale monitoring schemes in the United States, Canada, Great Britain, Sweden, and currently in the Netherlands and Switzerland. Modification, improvements and standardization of the original Williams’ mapping method led to the development of six different types of the mapping method: Consecutive Flush, International Standard, Combined Version, Total Mapping, Circular Mapping and Digital Mapping methods. Clustering (amalgamation) algorithms have been used to reduce human subjectivity in interpreting species maps. Imperfect bird detection during surveys was identified as a major source of bias in bird monitoring. Various mixture models were developed to solve this problem and helped to improve the accuracy of estimating population abundance, trends and species richness. Inter‐observer and inter‐analyst variability was identified as a major source of bias in mapping method estimates. Mapping methods vary widely in accuracy, and results differ among species and regions. Total Mapping, usually applied to single or few populations, can produce the most realistic population estimates. The Combined Version is considered one of the most accurate methods for territorial species and may be the most useful for more precise assemblage‐wide studies. Future development of these techniques should involve testing mapping efficiency and accuracy for individual species and determining the variability of estimates among species, habitats, seasons and observers, as well as the development of new algorithms for computerized evaluation of species maps and statistical models for correcting imperfect detection in monitoring surveys.
Point counts are a fundamental tool in avian ecology, yet the consequences of changing count duration remain poorly quantified, particularly across seasons and spatial scales. Using 660 time‐partitioned point‐count visits at 220 points in six Italian cities during the breeding and wintering seasons, we assessed the effect of reducing count duration from 10 to 5 min on per‐visit ( α ) and city‐wide ( γ ) species‐richness and on abundance, and tested whether losses were predicted by species traits. Five‐minute counts captured 81% of point‐level richness during breeding and 77% in winter, and missed up to 20% of the species recorded city‐wide by 10‐min counts in winter; winter losses were concentrated in migratory and small‐bodied species, whereas abundance retention (c. 81%) did not differ between seasons. Five‐minute counts may therefore suffice for abundance indices of common species, but not for describing community composition.
We conducted an integrative analysis to explore possible explanations for the song differentiation in bird populations from the mainland and the Tres Marías Archipelago (TMA) on the central‐western Pacific coast of Mexico. We first analysed the effect of isolation on cultural transmission by comparing repertoire size and genetic fixation in four phylogenetically distantly related passerines for which previous studies have documented significant genetic divergence between island and mainland populations. Then, we examined the contributions of potential factors involved in song differentiation (syllable duration and frequencies, frequency range), including morphology (bill size and body weight), genetic divergence and environmental factors (precipitation and temperature). Syllable sharing between TMA and mainland populations was higher for Northern Cardinals Cardinalis cardinalis and Golden Vireos Vireo hypochryseus but lower for Rufous‐backed Thrushes Turdus rufopalliatus . Songs of TMA populations showed longer syllable duration in Rufous‐backed Thrush and Golden Vireo, and shorter syllable duration in Northern Cardinal than those on the mainland. No significant differences were found between island and mainland populations of Streak‐backed Oriole Icterus pustulatus . Bill volume differed significantly between TMA and mainland populations of Northern Cardinals and Rufous‐backed Thrushes but not Streak‐backed Orioles and/or Golden Vireos. Correlations between body size and song frequencies were low but significant for most variables. We conclude that bird song differentiation on these islands is driven by isolation, environmental factors and morphology.
