Not Always Black and White: Colour Aberrations in the Dovekie

We describe four records of colour aberrations in the dovekie (Alle alle). During six years of studies of breeding ecology in two large dovekie colonies in West Spitsbergen, we recorded one albino chick (white feathers, red eyes, pinkish legs and feet), one adult or subadult with a “brown” aberration (all black parts turned dark brown), one adult in a typical summer plumage with depigmented (pinkish) legs and feet, and one chick in a typical plumage, but with whitish feathers on back and wing coverts. Albinism and “brown” mutations are heritable traits. The two remaining colour aberrations probably have been acquired and might have been caused by disease, malnutrition, or other unknown factors.Nous décrivons quatre mentions d’aberrations de couleur chez le mergule nain (Alle alle). Au cours de six années d’étude en écologie des oiseaux nicheurs au sein de deux grandes colonies de mergules nains de Spitzberg Ouest, nous avons dénoté un oisillon albinos (ailes blanches, yeux rouges, pattes et pieds rosés), un adulte ou jeune adulte doté d’une aberration « brune » (toutes les parties noires étaient devenues brunes), un adulte au plumage d’été typique et avec pattes et pieds dépigmentés (rosés) et un oisillon avec plumage typique, mais doté de plumes blanchâtres sur le dos et la couverture alaire. L’albinisme et les mutations « brunes » sont des caractères héréditaires, tandis que les deux autres aberrations de couleur ont probablement été acquises et peuvent être le résultat de maladie, de malnutrition ou d’autres facteurs inconnus

Glaucous Gull Predation on Dovekies: Three New Hunting Methods

We describe three previously unreported methods that hunting glaucous gulls (Larus hyperboreus) use to capture nesting and fledgling dovekies (Alle alle). During the nesting period, the pale-gray and white gulls camouflaged themselves by perching with head lowered on remnant snow patches in the dovekie colony, trying to ambush flying adults. We observed two other glaucous gull hunting methods on the open fjord water after the dovekie fledglings had left the colony. Gulls approached young dovekies in a fast, low-level glide, presumably to surprise the prey, and attempted to snatch them from the water. Gulls also swam rapidly towards young dovekies, zigzagging among small ice floes, presumably to confuse the birds and catch them before they could dive. The methods described, representing technical foraging innovations, supplement the evidence that gulls are a bird family that displays a diverse foraging innovation repertoire.Nous décrivons trois méthodes jamais signalées auparavant auxquelles recourent les goélands bourgmestres (Larus hyperboreus) pour capturer les mergules nains (Alle alle) aux stades de la nidification et de l’envol. Pendant la période de nidification, les goélands gris clair et blancs se camouflagent en se rabaissant la tête dans les restes de bancs de neige au sein des colonies de mergules nains afin d’essayer de piéger les adultes capables de voler. Nous avons observé deux autres méthodes de chasse de la part des goélands bourgmestres sur les eaux libres du fjord une fois que les mergules nains prêts à l’envol ont quitté la colonie. Les goélands s’approchaient des jeunes mergules nains en glissant rapidement et à faible altitude, vraisemblablement pour surprendre leurs proies, et essayaient de les arracher de l’eau. Les goélands se mettaient aussi à nager rapidement vers les jeunes mergules nains, en zigzaguant entre les bancs de glace flottante, probablement pour mélanger les oiseaux et pour les attraper avant qu’ils n’aient le temps de plonger. Les méthodes ainsi décrites, qui représentent des innovations techniques de chasse, s’ajoutent aux preuves qui attestent du fait que les goélands constituent une famille d’oiseaux dotée d’un répertoire de chasse innovateur et varié

Consequences of Atlantification on a Zooplanktivorous Arctic Seabird

Global warming, combined with an increasing influence of Atlantic Waters in the European Arctic, are causing a so-called Atlantification of the Arctic. This phenomenon is affecting the plankton biomass and communities with potential consequences for the upper trophic levels. Using long-term data (2005-2020) from a high Arctic zooplanktivorous seabird, the little auk (Alle alle), we tested the hypothesis that the Atlantification affects its diet, body condition and demography. We based our study on data collected in three fjords in West Spitsbergen, Svalbard, characterized by distinct oceanographic conditions. In all three fjords, we found a positive relationship between the inflow of Atlantic Waters and the proportion of Atlantic prey, notably of the copepod Calanus finmarchicus, in the little auk chick diet. A high proportion of Atlantic prey was negatively associated with adult body mass (though the effect size was small) and with chick survival (only in one fjord where chick survival until 21 days was available). We also found a negative and marginally significant effect of the average proportion of Atlantic prey in the chick diet on chick growth rate (data were available for one fjord only). Our results suggest that there are fitness costs for the little auk associated with the Atlantification of West Spitsbergen fjords. These costs seem especially pronounced during the late phase of the chick rearing period, when the energetic needs of the chicks are the highest. Consequently, even if little auks can partly adapt their foraging behaviour to changing environmental conditions, they are negatively affected by the ongoing changes in the Arctic marine ecosystems. These results stress the importance of long-term monitoring data in the Arctic to improve our understanding of the ongoing Atlantification and highlight the relevance of using seabirds as indicators of environmental change.publishedVersio

Consequences of Atlantification on a Zooplanktivorous Arctic Seabird

Global warming, combined with an increasing influence of Atlantic Waters in the European Arctic, are causing a so-called Atlantification of the Arctic. This phenomenon is affecting the plankton biomass and communities with potential consequences for the upper trophic levels. Using long-term data (2005-2020) from a high Arctic zooplanktivorous seabird, the little auk (Alle alle), we tested the hypothesis that the Atlantification affects its diet, body condition and demography. We based our study on data collected in three fjords in West Spitsbergen, Svalbard, characterized by distinct oceanographic conditions. In all three fjords, we found a positive relationship between the inflow of Atlantic Waters and the proportion of Atlantic prey, notably of the copepod Calanus finmarchicus, in the little auk chick diet. A high proportion of Atlantic prey was negatively associated with adult body mass (though the effect size was small) and with chick survival (only in one fjord where chick survival until 21 days was available). We also found a negative and marginally significant effect of the average proportion of Atlantic prey in the chick diet on chick growth rate (data were available for one fjord only). Our results suggest that there are fitness costs for the little auk associated with the Atlantification of West Spitsbergen fjords. These costs seem especially pronounced during the late phase of the chick rearing period, when the energetic needs of the chicks are the highest. Consequently, even if little auks can partly adapt their foraging behaviour to changing environmental conditions, they are negatively affected by the ongoing changes in the Arctic marine ecosystems. These results stress the importance of long-term monitoring data in the Arctic to improve our understanding of the ongoing Atlantification and highlight the relevance of using seabirds as indicators of environmental change.publishedVersio

Who bullies whom at a garden feeder? Interspecific agonistic interactions of small passerines during a cold winter

Interspecific agonistic interactions are important selective factors for maintaining ecological niches of different species, but their outcome is difficult to predict a priori. Here, we examined the direction and intensity of interspecific interactions in an assemblage of small passerines at a garden feeder, focussing on three finch species of various body sizes. We found that large and mediumsized birds usually initiated and won agonistic interactions with smaller species. Also, the frequency of fights increased with decreasing differences in body size between the participants. Finally, the probability of engaging in a fight increased with the number of birds at the feeder

Six pelagic seabird species of the North Atlantic engage in a fly-and-forage strategy during their migratory movements

Bird migration is commonly defined as a seasonal movement between breeding and non-breeding grounds. It generally involves relatively straight and directed large-scale movements, with a latitudinal change, and specific daily activity patterns comprising less or no foraging and more traveling time. Our main objective was to describe how this general definition applies to seabirds. We investigated migration characteristics of 6 pelagic seabird species (little auk Alle alle, Atlantic puffin Fratercula arctica, common guillemot Uria aalge, Brünnich’s guillemot U. lomvia, black-legged kittiwake Rissa tridactyla and northern fulmars Fulmarus glacialis). We analysed an extensive geolocator positional and saltwater immersion dataset from 29 colonies in the North-East Atlantic and across several years (2008-2019). We used a novel method to identify active migration periods based on segmentation of time series of track characteristics (latitude, longitude, net-squared displacement). Additionally, we used the saltwater immersion data of geolocators to infer bird activity. We found that the 6 species had, on average, 3 to 4 migration periods and 2 to 3 distinct stationary areas during the non-breeding season. On average, seabirds spent the winter at lower latitudes than their breeding colonies and followed specific migration routes rather than non-directionally dispersing from their colonies. Differences in daily activity patterns were small between migratory and stationary periods, suggesting that all species continued to forage and rest while migrating, engaging in a ‘fly-and-forage’ migratory strategy. We thereby demonstrate the importance of habitats visited during seabird migrations as those that are not just flown over, but which may be important for re-fuelling.publishedVersio