A flyway perspective on food resource abundance in a long-distance migrant, the Eurasian teal (Anas crecca)

Abstract

International audienceTwo frequent assumptions about the evolution of long-distance migration in birds are that they travel long distances annually to reach food-rich areas for breeding, and that they time their migratory journey to be at staging sites when the latter provide the best feeding conditions. These assumptions have rarely been properly tested, and there is no study in which a species' major food types have been measured by standardized methods throughout a flyway and over a large part of the year. We here present such data for Eurasian teal (Anas crecca), converted to a common energetic currency, and collected at wintering, spring staging and breeding sites. Teal did not time migration to maximize local food abundance; most birds left wintering and spring staging sites before a sharp increase in invertebrate food abundance occurred. On the other hand, hatching of ducklings coincided with a peak in invertebrate food abundance on boreal breeding lakes. Mean overall food abundance (invertebrates and seeds combined) did not differ between wintering sites in southern France and breeding sites in northern Sweden at the time of breeding. Our results are inconsistent with the hypothesis that long-distance migration in dabbling ducks has evolved because adult birds gain an immediate pay-off in increased food abundance by flying north in spring. However, our data confirm a selective advantage for breeding at higher latitudes, because hatching of ducklings may coincide with a peak in invertebrate emergence and because longer days may increase the duration of efficient foraging

Geographical and temporal patterns in the diet of pintail Anas acuta, wigeon Anas penelope, mallard Anas platyrhynchos and teal Anas crecca in the Western Palearctic

“…Most European countries have no studies of the diet of breeding ducks (Fig. 1), but Finland is a noteworthy exception (Pirkola 1966;Tiussa 1972;Nummi 1990Nummi , 1993Väänänen and Nummi 2003).The diet of dabbling ducks can be expected to vary seasonally depending on nutritional requirements as well as on the availability of different food taxa (Thompson et al 1992;Arzel et al 2009). For example, during spring and summer, females and ducklings require energy and protein-rich food (mostly invertebrates) for egg production and growth (Alisauskas and Ankney 1992).…”

“…Thus, item counts are not ideal when assessing the relative importance of different food types in terms of energy, and they need to be complemented by data on energetic content (e.g. Arzel et al 2007Arzel et al , 2009. However, there are other types of measures of duck diet that can be used to more accurately quantify diet items.…”

“…However, due to pronounced migratory habits and seasonal breeding of waterfowl, food and feeding mode are likely to vary considerably over the year as well as among geographical regions (Hartman 1985;Arzel et al 2009). Another important aspect is that young of many species have a diet that differs from that of adults (Sedinger 1992).…”

Resource tracking within and across continents in long-distance bird migrants

“…Resource availability is likely to be most important during breeding; thus, timing of breeding in relation to resource availability will be more important than stopover timing. Arrival well before the peak in insect prey abundance is common in migrants ( 28 , 29 ), and it may be impossible to consistently maximize local resources throughout the annual cycle.…”

Hatching in dabbling ducks and emergence in chironomids: a case of predator–prey synchrony?

“…The breeding period of dabbling ducks, however, may not be as easily adapted to seasonal changes in food abundance at the breeding site. One important reason is that any such adaptation has to be traded off against selective pressures acting in other biomes and at other times of the annual cycle (Arzel et al, 2007(Arzel et al, , 2009.…”