Veli-Matti Pakanen, Donald Blomqvist, Torgrim Breiehagen, Lars-Åke Flodin, Olavi Hildén, David B. Lank, Mikael Larsson, Terje Lislevand, Kimmo Nuotio, Peter Olsson, Richard Ottvall, Angela Pauliny, Hannes Pehlak, Antti Rönkä, Nelli Rönkä, Douglas Schamel, Martti Soikkeli, Robert L. Thomson, Ole Thorup, Pavel Tomkovich, Diane Tracy, Kari Koivula
Ardea 107 (1), 61-74, (8 May 2019) https://doi.org/10.5253/arde.v107i1.a9
KEYWORDS: Calidris alpina schinzii, Calidris temminckii, enlarged clutch, intraspecific nest parasitism, quasi-parasitism, Polygyny, shorebird, wader
Supernormal clutches are found across bird species. Such clutches often result from more than one female laying eggs in the same nest and can reflect different behaviours from parasitism to laying mistakes. Enlarged clutches are readily visible among waders due to a maximum maternal clutch size of four eggs, yet surprisingly little is known about this phenomenon. Since supernormal clutches are rare, large sample sizes are required to reliably quantify their natural frequencies. We used a large dataset to estimate the frequency of supernormal clutches in the polygamous Temminck's Stint Calidris temminckii and the monogamous Southern Dunlin C. alpina schinzii, and examine the timing of supernormal clutches in relation to the general distribution of nest initiation dates. While supernormal clutches were very rare, they were over four times more common in the Temminck's Stint (0.50%, n = 1594) than in the Southern Dunlin (0.11%, n = 2766). Dunlin show among the lowest frequency of supernormal clutches reported for waders. In the Temminck's Stint, supernormal clutches were found in the middle of the season, while in the Southern Dunlin such clutches occurred in late season replacement nests. The higher rate and timing of enlarged clutches in Temminck's Stints probably relates to the lspecies' breeding system, which can include simultaneous courtship of multiple partners, but more work is needed to assess the relative influence of different factors. We argue that intraspecific nest parasitism is unlikely to be a primary reproductive tactic in small sandpipers.