A long photoperiod overrides non-photoperiodic factors in blue tits' timing of reproduction

Abstract

Endocrinological studies have contributed considerably to the development of theory concerning the proximate aspects of the timing of reproduction. In non-domesticated, avian species, the relative importance of the photoperiodic and non-photoperiodic factors in£uencing later stages of the breeding cycle, such as the onset of egg laying, remains unclear because egg laying is di¤cult to obtain with captive populations and laboratory experiments of breeding are rarely carried out in the framework of long-term ¢eld studies. We set up a special experimental design such that captive Mediterranean blue tits (Parus caeruleus) can breed with success in large outdoor aviaries at similar latitudes and altitudes to their wild counterparts. Here we demonstrate experimentally that the non-photoperiodic factors responsible for large and consistent di¡erences in the expression of natural breeding responses between three captive outdoor blue tit populations are ignored during long-day treatment. Based on these ¢ndings, an evolutionary explanation is provided for why the relative importance of the non-photoperiodic factors decreases with the progress of the season. The hypothesis can explain observed maladapted breeding dates in free-living populations and could possibly be used to increase the success of breeding programmes with some endangered, captive, non-domesticated, photoperiodic species.

Why climate change will invariably alter selection pressures on phenology

“…Phenotypically plastic traits can obviously respond to more than one environmental variable, for example, seasonal timing of breeding in passerines depends on both ambient temperature and day length [41,42]. Assuming in our model that consumer phenology depends on more than one environmental variable would only make equation (2.5) more complex and hence lead to an even more restricted set of conditions that lead to no selection on consumer phenology.…”

Breeding Performance of Blue Tits Cyanistes caeruleus ultramarinus in Relation to Habitat Richness of Oak Forest Patches in North-Eastern Algeria

“…Thus, in these heterogeneous landscapes, where the different oak habitats are situated at similar altitude and exposed to similar ambient temperatures, the reproductive system of Blue Tits (e.g. see Caro et al 2006) does not seem to be sufficiently plastic to allow adaptive breeding time responses to very contrasting oak habitat types, most probably caused by maladapted photoperiodic responses in evergreen habitat (Lambrechts et al 1997b, Lambrechts & Perret 2000. However, the oak-caterpillar-tit ecosystem is known to be temperature-sensitive (e.g.…”

The Relevance of Environmental Conditions for Departure Decision Changes en Route in Migrating Geese

“…Second, proper choice of the relevant climatic parameters has to be inferred from a large number of possibilities, where a multitude of combinations are also possible. For example, it has frequently been shown that local temperatures are important for timing of breeding in birds (McCleery and Perrins 1998, Meijer et al 1999, Both et al 2004, Brommer et al 2005, but day length can also play a role (Lambrechts and Perret 2000). Ideally, therefore, several variables need to be explored simultaneously.…”