GPS tracking data of Eurasian oystercatchers (Haematopus ostralegus) from the Netherlands and Belgium

We describe six datasets that contain GPS and accelerometer data of 202 Eurasian oystercatchers (Haematopus ostralegus) spanning the period 2008–2021. Birds were equipped with GPS trackers in breeding and wintering areas in the Netherlands and Belgium. We used GPS trackers from the University of Amsterdam Bird Tracking System (UvA-BiTS) for several study purposes, including the study of space use during the breeding season, habitat use and foraging behaviour in the winter season, and impacts of human disturbance. To enable broader usage, all data have now been made open access. Combined, the datasets contain 6.0 million GPS positions, 164 million acceleration measurements and 7.0 million classified behaviour events (i.e., flying, walking, foraging, preening, and inactive). The datasets are deposited on the research repository Zenodo, but are also accessible on Movebank and as down-sampled occurrence datasets on the Global Biodiversity Information Facility (GBIF) and Ocean Biodiversity Information System (OBIS)

Variation in habitat choice and delayed reproduction: Adaptive queuing strategies or individual quality differences?

In most species, some individuals delay reproduction or occupy inferior breeding positions. The queue hypothesis tries to explain both patterns by proposing that individuals strategically delay breeding (queue) to acquire better breeding or social positions. In 1995, Ens, Weissing, and Drent addressed evolutionarily stable queuing strategies in situations with habitat heterogeneity. However, their model did not consider the non - mutually exclusive individual quality hypothesis, which suggests that some individuals delay breeding or occupy inferior breeding positions because they are poor competitors. Here we extend their model with individual differences in competitive abilities, which are probably plentiful in nature. We show that including even the smallest competitive asymmetries will result in individuals using queuing strategies completely different from those in models that assume equal competitors. Subsequently, we investigate how well our models can explain settleme! nt patterns in the wild, using a long-term study on oystercatchers. This long-lived shorebird exhibits strong variation in age of first reproduction and territory quality. We show that only models that include competitive asymmetries can explain why oystercatchers' settlement patterns depend on natal origin. We conclude that predictions from queuing models are very sensitive to assumptions about competitive asymmetries, while detecting such differences in the wild is often problematic.

Towards a simplified approach for assessing bird food requirements on shellfisheries. A report to the Welsh Government.

In northwest Europe conflicts have routinely occurred between economic and conservation interests regarding shellfish such as cockles and mussels. The harvest of these species is economically important, but shellfish also constitute the main overwinter food supply of the oystercatcher Haematopus ostralegus. In this report we describe attempts to produced a simplified modelling approach to predict the quantities of shellfish which need to be left unharvested in order to ensure high overwinter survival of oystercatcher. We review oystercatcher diet and prey selection in order to quantify the dependence of this species on shellfish, and determine the size ranges of shellfish which the birds consume. We also review the food requirements of oystercatchers, based on their energetic needs and the nutritional quality of shellfish. In general the data agree well with those used in previous oystercatcher modelling studies. However, there is a possibility that the daily energy requirements, calculated from an all bird allometric equation, may yield an underestimate of oystercatcher food requirements. A comparison of the physiological food requirements, i.e. the quantity directly consumed, and the ecological food requirements, i.e. the quantity required to avoid high mortality, indicated that the ecological food requirement was between 2.0 and 7.8 times greater, with the value depending on the proportion of cockles Cerastoderma edule and mussels Mytilus edulis in a site. These ratios are calculated from empirical data on oystercatcher survival and the predictions of individual-based models predicting the relationship between mortality rate and the abundance of the food supply. Data from the Burry Inlet indicated that the mean ecological food requirement was 3.3 times greater at this site. We describe a simplified spreadsheet model, which we used to predict the food requirements of the oystercatcher population of the Burry Inlet, and thus the quantity of shellfish which must be left unharvested in order to maintain low mortality rate. The model is based on parameter values derived from the literature reviews in this study, including the energy requirements of the birds, the energy content of shellfish, the minimum size of cockles and mussels consumed, and the ratio of the ecological and physiological requirements. We describe the assumptions and limitations of the model, and compare the model with more detailed individual-based models that can be used to predict the mortality rate of shorebirds in relation to the amount of food available

Appearance, development of plumage and morphometric measurements in chicks of the Eurasian Oystercatcher Haematopus ostralegus from hatching to fledging

Die Arbeit behandelt die äußere Entwicklung von Küken des Austernfischers (Haematopus ostralegus) vom Schlüpfen bis zur Flugfähigkeit der Jungvögel im Schleswig-Holsteinischen Wattenmeer. Das Aussehen und die Veränderung von Dunenkleid, Schnabel, Beinen und Lidring sowie die Entwicklung des Gefieders vom ersten bis etwa zum 40. Lebenstag werden beschrieben und durch Fotos illustriert. Gewicht, Flügellänge, Schnabellänge und -höhe von ein-, 18- und 30-tägige Küken werden angegeben. Mehr als 40 Küken wurden nach dem Schlüpfen markiert und ihre Entwicklung bis zum Flüggewerden verfolgt. Am ersten Tag nach dem Schlüpfen trocknet das kontrastreiche Dunenkleid. Die Beine sind zuerst hell fleischfarben, verfärben sich aber schnell blaugrau. Der Schnabel ist mehrfarbig weiß, grau und schwarz und besitzt eine rosa Basis. Bis zum etwa 14. Tag tragen die Küken ein hell sandfarbenes Dunenkleid mit schwarzer Zeichnung. Der Eizahn fällt am dritten oder vierten Tag ab. Die ersten Handschwingen durchbrechen am elften Tag die Blutkiele. Der Schnabel ist dann dunkel braunschwarz mit oranger Unterschnabelbasis. Ab dem etwa 15. Tag wirkt das Dunenkleid deutlich dunkler, was durch nachschiebendes dunkles Gefieder verursacht wird. Der Kontrast der schwarzen Zeichnung nimmt ab. Der Schnabel verfärbt sich zunehmend orange und die Umfärbung des Lidrings zu dunkelgelb beginnt. Ab ca. dem 20. Tag sind auf den meisten Körperpartien die Federn des Jugendkleids durchgebrochen. Dunenreste bleiben noch länger, vor allem auf Kopf und Rücken auffällig. Die Umfärbung des Lidrings wird abgeschlossen und sehr langsam verfärben sich die Beine fleischfarben. Ab ca. dem 30 Tag erscheinen die Jungvögel voll befiedert, man findet aber noch kleinflächige Dunenreste. Der Schnabel ist dann orange mit dunkler Spitze und dunklerem Oberschnabelfirst. Die Umfärbung der Beine wird erst später deutlich. Ab etwa dem 40. Tag sind kaum mehr Dunen zu erkennen. Kopf, Hals, Brust und Oberseite der jetzt flugfähigen Jungvögel sind größtenteils dunkelbraun, nur ein dünner heller Kragen bleibt erhalten. Die Unterseite ist weiß.The paper describes the external changes of chicks of the Eurasian Oystercatcher (Haematopus ostralegus) from hatching to fledging. The downy plumage, bill, legs and eye-ring and the growth of plumage from the first until about the 40th day of life are treated and illustrated by photos. Average weight, wing lenght, bill length and bill depth are listed for one, eighteen and thirty days old chicks. More than 40 chicks had been tagged after hatching on Hamburger Hallig/North Frisia (Schleswig- Holstein) and their development was followed therefrom. On the first day after hatching, the contrasting downy plumage dries. Legs are light pinkish at first, soon changing to bluish grey. The bill is multi-coloured white, grey and black with a pink base. Up to c. the 14th day, chicks have a light, sandy downy plumage with black markings. The egg-tooth drops on the third or fourth day. The first primaries break through on the eleventh day. The bill is now dark brownish black with orange lower mandible. From c. the 15th day onwards, the downy plumage appears much darker, caused by dark feathers developping under the downs. The contrast of black markings decreases. The bill changes colour, getting more orange and the colour of the eye-ring starts to change to dark yellow. From about the 20th day, feathers of the juvenile plumage are found on most parts of the body. Remains of the downy plumage are still obvious, especially on the head and back. The eye-ring gets all yellow and the color of legs slowly starts to change to pink. From about the 30th day, juveniles appear fully feathered, showing only few remnants of downs. The bill is orange with a darker tip and darker ridge of the upper mandible. The change of colour of the legs becomes obvious only later. From ca. the 40th day onwards, hardly any downs are visible. The juveniles are now able to fly. Their head, neck, breast and upperparts are largely dark brown and a thin, ligth collar remains. The underparts are now white