Of all arctic breeding waders, Little Stints are among the smallest. They are uniparental breeders: the female produces two clutches and the male and female each take care of one clutch (fig. 1). The combination of their small size, arctic distribution and uniparental breeding system results in an energetically very expensive way of life. During three field seasons in Taimyr, Siberia, we studied how Little Stints cope with this. At the onset of breeding the eggs are laid in a nest cup which is very close to the permafrost layer (fig. 2). Little Stints fill up their nest cup with a thick layer of dwarf willow leaves, the best insulative material that can be found in the tundra. Compared to other arctic wader species co-occuring in the same area, the nest cup is also deeper and the lining thicker, resulting in a better isolated nest. During incubation Little Stints carry larger energy stores than during chick-rearing. However these are not sufficient to last the whole incubation period. These stores function as an insurance for periods of bad weather, when they allow the birds to maintain a high nest attentiveness despite a negative energy balance. Little Stints alternative incubation with numerous short feeding bouts (fig. 3). During the coldest part of the 'night' they incubate continuously. On cold days they make fewer but longer feeding trips, resulting in a decrease in time spent incubating and more time available for foraging. Nevertheless, a relationships between body mass and the weather in the preceding days shows up in Little Stint, but not in the biparentally breeding Dunlin, indicating that Little Stints use their reserves more often (fig. 5). In accordance with the view that the size of energy stores reflects risk of starvation, these stores are larger in Little Stints than in larger wader species and also increase with breeding latitude (fig. 4). Food available for both adults and chicks strongly depends on weather but also shows a clear seasonal pattern. Chick growth rates are correlated with food availability (fig. 6). To optimise chick growth, hatching should take place at or close to the peak of arthropood abundance. For uniparental breeders, having to allocate time to both incubation and feeding, food availability during incubation must also allow sufficiently high intake rates. This might explain why uniparental arctic shorebirds start breeding later compared to biparental species. In our studies we mainly concentrated on the (energetic) costs of the uniparental breeding system. The Little Stints is one of the few arctic breeding shorebirds that use this strategy. The reason why not more species use this energetically expensive system, is likely to be found in the balance between costs and benefits (reproductive success) that apparently works out differently for different species.
|Translated title of the contribution||Great achievements by Little Stints Calidris minuta|
|Number of pages||10|
|Publication status||Published - Dec 2004|