Simulated moult reduces flight performance but overlap with breeding does not affect breeding success in a long‐distance migrant

Abstract

Long‐distance migrants are time‐constrained as they need to incorporate many annual cycle stages within a year. Migratory passerines moult in the short interval between breeding and migration. To widen this interval, moult may start while still breeding, but this results in flying with moulting wings when food provisioning. We experimentally simulated wing gaps in breeding male pied flycatchers by plucking two primary feathers from both wings. We quantified the nest visitations of both parents, proportion of high‐quality food brought to the nestlings and adults and nestlings condition. Differences in oxidative damage caused by a possible reduction in flight efficiency were measured in amounts of ROMs and OXY in the blood. We also measured how flight performance was affected with recordings of the male`s escape flight using high‐speed cameras. Finally, we collected data on adult survival, clutch size and laying date in the following year. “Plucked” males travelled a 5% shorter distance per wingbeat, showing that our treatment reduced flight performance. In line with this, “plucked” males visited their nests less often. Females of “plucked” males, however, visited the nest more often than controls, and fully compensated their partner's reduced visitation rate. As a result, there were no differences between treatments in food quality brought to the nest, adult or chick mass or number of successfully fledged chicks. Males did not differ in their oxidative damage or local survival to the following year. In contrast, females paired with plucked males tended to return less often to breed in the next year in comparison to controls, but this difference was not significant. For the birds that did return, there were no effects on breeding. Our results reveal that wing gaps in male pied flycatchers reduce their flight performance, but when it occurs during breeding they prioritise their future reproduction by reducing parental care. As a result, there is no apparent detriment to their condition during breeding. Because non‐moulting females are able to compensate their partner's reduced care, there is also no immediate cost to the offspring, but females may pay the cost suffering from a reduced survival. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.12974/suppinfo is available for this article.

Life‐history innovation to climate change: can single‐brooded migrant birds become multiple breeders?

“…Although sample sizes are low, we have no indication that female return rates were lower for double breeding females in the Swiss population, as 50% of them returned to the following year, which is comparable to the overall return rate (Ravussin et al ). One out of the three females that produced a second brood in Drenthe in returned as breeder in , again comparable to the overall female return rate (which was 0.26). It is noteworthy that one Swiss female produced second broods in two subsequent years.…”

“…Also in Vaud multiple breeding females were in the early tail of the laying distribution, all starting before 4 May. In 1980–1990 only a single female was observed to lay this early (0.4%), whereas between 2003 and 12% of females (n = 611) started laying before 4 May.…”

“…Therefore, we regard the occurrence of these second broods in most cases not as a best‐of‐a‐bad‐job strategy after producing poorly during the first breeding attempt. Indeed, the three Dutch second broods in produced 13 fledglings, of which one (male) recruit was observed as breeder in (average first year recruitment rate is 4%).…”

“…1, Table 1). To place this timing into perspective, in Drenthe, four double‐breeding females started laying before 25 April, whereas between and only 1.3% of the clutches started before this date. In the period 1980–1990, only 0.18% of clutches were initiated this early, and for 1991–2000 it was 0.16%.…”

“…In the other cases the interval between hatching of the first brood and start of laying of the second brood was 15–25 d, and was 5 d longer in Vaud than in Drenthe (21.4 (SE:1.0) versus 16.8 (1.1), KW = 4.42, p = 0.04). As nestlings fledge around day 15, in most Dutch cases the female must have started nest building and growing follicles before the chicks left the nest, and females unlikely participated in post‐fledging care, or even abandoned the nest prior to fledging (at least observed in the case in ).…”