Breeding Biology of Steller's Eiders (<i>Polysticta stelleri</i>) near Barrow, Alaska, 1991–99

Abstract

ABSTRACT. The breeding biology of Steller's eiders (Polysticta stelleri) near Barrow, Alaska, was studied from 1991 to 1999. The number of nests found per year ranged from 0 to 78. Mean clutch size was 5.4 (SD = 1.6, n = 51), incubation period was 24 days, and Mayfield nest success ranged from 0 to 35%. Egg survival was 24% overall (n = 451). Most nests were found on the rims of low-centered polygons near ponds with emergent vegetation. Marked broods remained within 700 m of their nest sites, and duckling survival was low. Steller's eiders nested in five of the nine years studied, corresponding with years of high lemming density and nesting pomarine jaegers (Stercorarius pomarinus) and snowy owls (Bubo scandiacus). Steller's eiders may choose to nest only in years with abundant lemmings for two reasons: first, abundant lemmings provide an alternative prey source for foxes and other predators of eiders; second, jaegers and owls defending their own nests may inadvertently provide protection to eiders nesting nearby.Key words: Alaska, Steller's eider, Polysticta stelleri, nesting success, habitat selection, nesting associations, periodic nonbreeding RÉSUMÉ. De 1991 à 1999, on a étudié la biologie de reproduction de l'eider de Steller (Polysticta stelleri) près de Barrow, en Alaska. Le nombre de nids trouvés annuellement allait de 0 à 78. La taille moyenne de la couvée était de 5,4 (écart type = 1,6, n = 51), la période d'incubation était de 24 jours et le succès de la couvée calculé selon la méthode de Mayfield allait de 0 à 35 %. La survie des oeufs était dans l'ensemble de 24 % (n = 451). La plupart des nids étaient situés sur le bord de polygones concaves près d'étangs avec une végétation émergente. La progéniture marquée restait dans les 700 m du site du nid, et la survie des canetons était faible. L'eider de Steller a niché cinq ans sur les neuf de l'étude, soit ceux correspondant aux années où il y avait une forte densité de lemmings, ainsi que de nids de labbes pomarins (Stercorarius pomarinus) et de harfangs des neiges (Bubo scandiacus). Il se pourrait que l'eider de Steller choisisse de ne se reproduire que durant les années d'abondance de lemmings pour deux raisons: la première, c'est qu'une abondance de lemmings offre une source alternative de proies pour les renards et d'autres prédateurs de l'eider; la deuxième, c'est que les labbes pomarins et les harfangs qui défendent leurs propres nids pourraient, involontairement, offrir une protection aux eiders qui nichent à proximité.Mots clés: Alaska, eider de Steller, Polysticta stelleri, réussite de la couvée, sélection de l'habitat, association de nidification, nonreproduction périodique Traduit pour la revue

Seasonal Movements and Distribution of Steller’s Eiders (<i>Polysticta stelleri</i>) Wintering at Kodiak Island, Alaska

“…Arrival dates appeared to vary annually, likely because timing of nesting in Steller's Eiders is thought to be highly correlated with annual variability in snowmelt (Solovieva, 1999;Quakenbush et al, 2004). Staging for short periods at multiple locations before arrival at nesting areas may allow Steller's Eiders to assess local conditions in order to optimize nest initiation relative to habitat availability.…”

“…However, non-instrumented females are known to forgo breeding in some years (Ankney and Alisauskas, 1991). For example, Steller's Eiders observed on some localized breeding areas in Arctic Russia and Alaska appear to nest primarily in years of high microtine abundance when nomadic breeding species like jaegers and Snowy Owls are also nesting, which results in an irregular pattern that includes some nesting years and some non-nesting years (Solovieva, 1999;Quakenbush et al, 2004). Steller's Eiders may increase individual fitness by limiting reproductive effort to years when conditions are favorable (Quakenbush et al, 2004).…”

“…For example, Steller's Eiders observed on some localized breeding areas in Arctic Russia and Alaska appear to nest primarily in years of high microtine abundance when nomadic breeding species like jaegers and Snowy Owls are also nesting, which results in an irregular pattern that includes some nesting years and some non-nesting years (Solovieva, 1999;Quakenbush et al, 2004). Steller's Eiders may increase individual fitness by limiting reproductive effort to years when conditions are favorable (Quakenbush et al, 2004). However, it is unknown whether birds forfeit nesting in years when they do not breed at these localized areas or simply attempt to breed elsewhere in Alaska or in Russia.…”

“…A relatively large segment of the population (> 100 000 breeding birds; Hodges and Eldridge, 2001) breeds along the eastern Arctic coast of Russia. A much smaller number (< 1000 breeding birds; ) breeds almost exclusively on the Arctic Coastal Plain of Alaska, concentrated over a relatively small area near the village of Barrow (Pitelka, 1974;Flint and Herzog, 1999;Quakenbush et al, 2004). Both breeding segments of the Pacific population winter together, primarily in marine coastal waters of Alaska, from Cook Inlet and Kodiak Island westward along the Alaska Peninsula to the eastern Aleutian Islands (Fredrickson, 2001).…”

“…Accordingly, efforts have been made to better understand the biology of Steller's Eider and protect the species and its habitats (U.S. Fish and Wildlife Service, 2002). Recently, understanding has improved of basic demographics and distribution (Jones, 1965;Dau et al, 2000;Quakenbush et al, 2004), but many information gaps remain. Data that contribute to knowledge of migration routes and chronology, seasonal habitat use, and links among lifecycle stages provide valuable broad-scale information for identifying population-limiting factors and for developing conservation strategies.…”