POLYMORPHIC FLIGHT-FEATHER MOLT SEQUENCE IN TUFTED PUFFINS (FRATERCULA CIRRHATA): A RARE PHENOMENON IN BIRDS

Auk, The, Jan 2004 by Thompson, Christopher W, Kitaysky, Alexander S

ABSTRACT.-Previous reports have stated that Tufted Puffins (Fratercula cirrhata) lose all of their flight feathers simultaneously (or nearly so) during flight-feather molt and replace them in no apparent order. In contrast, we found that captive second-year (SY) Tufted Puffins (1) typically require 15 and 10 days to lose their primaries and secondaries, respectively, during their first flight-feather molt, and an average of 21 days to lose all of their remiges; and (2) replace their primaries in either of two discrete sequences. In 9 of 13 birds, primary molt began at the innermost primary, P1, and progressed distally to the outermost functional primary, P10. However, in the remaining four birds, primary molt began in the middle of the primaries (P5-P7) and progressed both distally to P10 and proximally toward P1. Before the proximal wave reached P1, a second wave of molt was initiated at P1 and progressed distally, typically replacing P2 and P3 before reaching the proximal wave. Such polymorphism in flight-feather molt sequence is rare in birds, having been reported previously only in a few passerine species. Secondary molt began about 13 days after onset of primary molt and finished at about the same time as primary molt, resulting in a total duration of flight-feather molt of ~54 days and a flightless period of ~40 days. Received 6 December 2001, accepted 7 September 2003.

RESUMEN.-Se ha establecido mediante reportes previos que las aves de la especie Fratercula cirrhata pierden todas sus plumas de vuelo simultaneamente (o casi) durante la muda de las plumas de vuelo, y que las reemplazan sin un orden aparente. En contraste, nosotros encontramos que individuos cavitivos en su segundo ano (1) requieren tipicamente 15 y 10 dias para perder sus plumas primarias y secundarias, respectivamente, durante su primera muda de las plumas del vuelo, y un promedio de 21 dias para perder todas sus renieras; y (2) reemplazan sus primarias en cualquiera de dos secuencias discretas. En nueve de 13 aves, la muda de las primarias comenzo en la primaria mas interna, P1, y progreso de modo distal hacia la primaria funcional mas externa, P10. Sin embargo, en las cuatro aves restantes la muda comenzo en las primarias de la mitad (P5-P7) y progreso de modo distal hacia P10 y proximal hacia P1. Antes de que la onda proximal Ilgara a P1, una segunda onda de muda se inicio en P1 y progreso de modo distal, reemplazando tipicamente a P2 y P3 antes de alcanzar la onda proximal. Este polimorfismo en la secuencia de muda de las plumas del vuelo es raro en las aves, y ha sido reportado previamente solo para unas pocas especies de paserinos. La muda de las secundarias comenzo aproximadamente 13 dias despues del comienzo de la muda de las primarias y termino casi al mismo tiempo que la muda de las primarias, resultando en una duracion total de la muda de las plumas del vuelo de ~54 dias y en un periodo de incapacidad de vuelo de ~40 dias.

MOLT, ESPECiALi1Y ov flight feathers, is an energetically expensive and time-consuming activity in the annual cycle of birds (Walsberg 1983, Murphy and King 1991, Murphy 1996, Klasing 1998). In addition, during flight-feather molt, the ability to fly is diminished by increased wing loading and by gaps in the wing where flight feathers are missing or regrowing, thereby increasing flight costs and vulnerability to predators. As a result, various aspects of the molting process are subject to strong natural selection. The tremendous diversity observed in (1) the site(s) at which flight-feather molt is initiated and (2) the sequence in which flight feathers are replaced in various species (Dwight 1900, 1925; Stresemann and Stresemann 1966; Ginn and Melville 1983; Baker 1993; Jenni and Winkler 1994; PyIe 1997a; Rohwer 1999) probably reflects both strong selection pressure and differences in species' life histories.

For example, most species of diving birds (e.g. loons [Gaviidae], most grebes [Podicipedidae], diving petrels [Pelecanoididae], darters and anhingas [Anhingidae], most waterfowl [Anseriformes], and medium-size to large alcids [Alcidae]) molt during the nonbreeding season while living on the ocean or other bodies of water. The literature regarding molt in those groups generally states that they lose all their remiges simultaneously or nearly so, implying that regrowth of remiges is also synchronous -that is, they are not replaced in any apparent order (Palmer 1962, 1972, 1976a, b, 1988a, b, 1988; Stresemann and Stresemann 1966; Cramp 1977, 1980, 1983, 1985, 1988, 1992, 1993, 1994a, b; Marchant and Higgins 199Oa, b, 1993; Wells 1999). In contrast, Thompson et al. (1998) recently found that Common Murres (Uria aalge) lose and replace their primaries rapidly but not simultaneously, and do both in a consistent, orderly fashion. Especially interesting is the unusual sequence of loss and replacement: primary molt begins at a single node in the middle of the primaries and proceeds in two concurrent waves, one proximally to Pl and the other distally to PlO. However, it is not known whether the sequence of flight-feather molt observed in Common Murres occurs in any other alcids or in other diving birds.