Timing of migration in Common Redstarts (Phoenicurus phoenicurus) in relation to the vegetation phenology at residence sites

Abstract

Timing the annual cycle according to local conditions is crucial for animals in seasonal environments, because individual resource requirements must match seasonal resource availabilities. Pre-nuptial spring migration is especially time constrained in many migratory species, and thus tight adjustments of departure and arrival times to local environmental conditions can be expected. We determined non-breeding residences of Common Redstarts, an insectivorous Palearctic-African migrant, from a central European population. Non-breeding residencies of three out of four males were located in the northern Sahel of WestAfrica; a single individual did not cross the Sahara desert, but spent the non-breeding season in Northern Africa instead. Additionally, we related local vegetation phenology and the timing of spring migration in a central and a northern European population differing largely in breeding site latitude. The arrival at and departure from the African sites was similar in birds from the central and the northern population. Departure from the non-breeding sites was not related to seasonal deterioration of vegetation. Birds from both populations arrived at their distant breeding grounds in the same time period. Since spring green-up times differed greatly, birds from the two populations encounter different phenological conditions at arrival. The missing relation between vegetation phenology and migration timing may indicate that spring migration in redstarts is triggered by other factors than vegetation development at least at the non-breeding sites. A general cue such as local photoperiod might be the candidate factor, which would also explain the small variation between the populations.

Limited flexibility in departure timing of migratory passerines at the East-Mediterranean flyway

“…In agreement with previous studies 67 , 90 , we could not link between local vegetation phenology and departure timing of the redstart from the African non-breeding grounds. Given the large range of redstart on the African non-breeding ground, it is likely that we failed to detect such a trend due to the insufficient range accuracy for the populations flying through Israel.…”

“…In addition, Newson, et al 86 present earlier arrival of redstart to breeding grounds in the UK between 2002–2011 than in the mid-1960s, and Porkert et al 62 demonstrated advanced egg-laying dates in nine Eurasian populations of the redstart. The advanced arrival of both sexes at the breeding ground, in contrast to the trend found only in males in Israel, may be a result of females adjusting migration speed en route 5 , 67 , 87 . Sexual differences in changes to migration timing were also shown in willow warbler Phylloscopus trochilus in Sweden, where males advanced arrival more strongly than females 84 .…”

“…The arrival day of barred warbler was also independent of spatial and temporal availability of resources during the pre-migratory period (measured as EVI). Combined with the relatively stable environmental conditions on its non-breeding ground during the study period, the decision when to depart on migration is likely more dominated by endogenous cues, photoperiod 22 , 33 , 67 or environmental variables other than vegetation growth 16 . While internal cues are fundamentals of the annual cycle in the evolution of migratory birds 24 , in the case of low phenotypic plasticity, it limits the ability of individuals to respond to climate change and risk its fitness and survival e.g.…”

“…For the redstart, we focused on the eastern part of its vast non-breeding range (east of 15.7 degrees), as the individuals from the western part are likely migrating to Europe via the western or central flyway e.g. 67 . Although there are generally two rainfall seasons, for the northern and southern part of Africa, the distribution of seasons vary considerably across Africa, mainly south of the equator 68 .…”

Resource tracking within and across continents in long-distance bird migrants

“…Such strategies could occur in several of the longest-distance migrating species wintering south of the equator, for example, marsh warblers ( Acrocephalus palustris ) ( 23 ), but are potentially more constrained in species wintering further north in, for example, West Africa, where resources generally decline from early fall ( 53 , 54 ). The species we tracked showed no consistent pattern in, whether birds experienced increasing or decreasing greenness.…”