Jeffrey S. Marks

Genetic monogamy in long-eared owls

We used DNA fingerprinting to study genetic parentage in socially monogamous Long-cared Owls (Asio otus). We detected no extra-pair fertilizations (EPFs) in 59 nestlings from 12 nests. One of these nests was solitary, but the other 11 had from one to five pairs of owls nesting simultaneously within 30 to 250 m. Thus, despite the presumably high potential for extra-pair matings, the Long-cared Owls that we studied were genetically monogamous. In addition, based on low band sharing among adults, we found no evidence that nesting aggregations were composed of close relatives. Genetic monogamy appears to be the rule for socially monogamous raptors. We suggest that the high rate of male parental effort in raptors selects against EPFs because females that engage in extra-pair activities risk losing parental investment by males whose confidence in paternity is reduced owing to the behavior of their mates.

Migration of Bristle-Thighed Curlews on Laysan Island: Timing, Behavior and Estimated Flight Range

Bristle-thighed Curlews (Numenius tahitiensis) fly at least 4,000 km non-stop from staging grounds in western Alaska to the northern edge of the winter range at Laysan Island in the Northwestern Hawaiian Islands. Adults migrate from Laysan in early May and return in July and August. Juveniles, which arrive in late August and early September, largely migrate unaccompanied by adults. Compared with other shorebirds, Bristle-thighed Curlews migrate in small flocks and show no diurnal pattern in timing of departures. Subadults do not fatten adequately for migration but often accompany departing adults briefly and then return to the island. Fat content in adults at the start of spring migration is high, averaging 42%. Our findings indicate that curlews wintering in the Central and South Pacific overfly Hawaii during spring and autumn, undertaking non-stop flights of >6,000 km. In the absence of tailwinds, only two of the four flight range models that we tested (Summers and Waltner 1979, Davidson 1984) provide reasonable estimates of the migratory performance of Bristle-thighed Curlews (i.e., non-stop flights from Alaska to Laysan and beyond). Within the range of altitudes at which they migrate, curlews probably seek out tailwinds that facilitate long-distance, non-stop flights.

Serial polyandry and alloparenting in long-eared owls

Abstract We used DNA fingerprinting to document serial polyandry in a double-brooded female Long-eared Owl (Asio otus) in western Montana. We also determined that an extra male that helped provision offspring at a nest was a close relative of the female parent. The nest had split paternity, and it is not clear whether the helper was the sire or brother of two of the four nestlings. These data constitute the first known cases of serial polyandry and alloparenting in Long-eared Owls and leave open the question of whether cooperative polyandry also occurs in this species. Poliandría en Serie y Alopaternidad en Asio otus Resumen. Empleamos huellas dactilares genéticas (i.e., DNA fingerprinting) para documentar poliandría en serie en una hembra de Asio otus que presentó dos nidadas, en el oeste de Montana. También determinamos que un macho extra-pareja que ayudó a abastecer a los pichones en un nido era un pariente cercano de la madre. El nido presentó paternidad compartida y no está claro si el ave que ayudaba era el padre o el hermano de dos de los cuatro polluelos. Estos datos representan el primer caso conocido de poliandría en serie y alopaternidad en Asio otus, y deja abierta la pregunta si en esta especie también ocurre poliandría cooperativa.