The flight feather moult pattern of the bearded vulture (Gypaetus barbatus)

Abstract

Moult is an extremely time-consuming and energy-demanding task for large birds. In addition, there is a trade-off between the time devoted to moulting and that invested in other activities such as breeding and/or territory exploration. Moreover, it takes a long time to grow a long feather in large birds, and large birds that need to fly while moulting cannot tolerate large gaps in the wing, but only one or two simultaneously growing feathers. As a consequence, large birds take several years to complete a full moult cycle, and they resume the moult process during suboptimal conditions. A clear example of this pattern is the Bearded Vulture (Gypaetus barbatus), which needs 2-3 years for changing all flight feathers. Here we describe the sequence, extent, and timing of moult of 124 Bearded Vultures in detail for the first time. We found that extent and timing of flight feather moult was different between age classes. Subadults (from 3rd to 5th calendar year)

Moult in Birds of Prey: A Review of Current Knowledge and Future Challenges for Research

“…For large birds, the difference between the power required for sustained flight and the maximum power available is relatively small, making flight with proportionately similar moult gaps than smaller birds impossible (Tucker, 1991). Therefore birds of prey, that fly while moulting, cannot compensate for the relatively slow growth of their remiges by replacing more primaries and secondaries simultaneously (Rohwer et al, 2011;Zuberogoitia et al, 2013;2016a).…”

“…Intraspecific variation in moult sequence, duration and extent depends, among other factors, on the breeding cycle; the age and sex of the bird; territory quality; the status (dispersive, floater, sedentary or migrant) of each individual; latitude; local weather and climatic variation (Ydenberg et al, 2007;Newton & Dawson, 2011;Dietz et al, 2013;Zuberogoitia et al, 2016a). Moreover, it must be considered that, once grown, each feather will normally be retained for at least a year, during which it will deteriorate progressively, due to environmental conditions and individual behaviour (Zuberogoitia et al, 2013).…”

“…Old and New World vultures exhibit the largest numbers of SS, with as many as 25 in Griffon Vultures Gyps fulvus (Ginn & Melville, 2000;Zuberogoitia et al, 2013). Bearded Vultures Gypaetus barbatus have a variable number of SS (19 or 20), possibly due to the absence of one of the innermost SS in some birds (Zuberogoitia et al, 2016a). The rectrices (RR) are numbered in pairs, from the central feathers (RR1) outwards.…”

Using field photography to study avian moult

“…, Ryan , Zuberogoitia et al . ). Keijl () suggested that photography might be a promising way to study moult in pelagic seabirds that are difficult to catch.…”

“…Newton 1966, Underhill & Zucchini 1988, Newton & Rothery 2009, Scherer et al 2013, Morrison et al 2015. However, such data may also be acquired with other methods such as photography, which has been used to study moult in marine mammals (McConkey et al 2002) and waders (Conklin & Battley 2011, 2012 Other studies used opportunistically taken photographs of birds in moult to complement information based on conventional methods (Snyder et al 1987, Ryan 2013, Zuberogoitia et al 2016. Keijl (2011) suggested that photography might be a promising way to study moult in pelagic seabirds that are difficult to catch.…”