Population dynamics of an expanding passerine at the distribution margin

Abstract

Individuals may be maladapted to novel environments at the species' distribution margin. We investigated population dynamics in a marginal habitat where reproduction has been proven poor. Survival, population growth rate (l) and its components, breeding and natal dispersal were studied in great tits Parus major breeding at the northern margin of its distribution in northern Finland. We used long term capture-mark-recapture data sets. Study area size and population density were used to explain adult survival rates. The average annual estimates of adult survival rose from 0.371 to 0.388 between the periods of 1971-1984 and 1999-2009. The estimates are slightly lower than estimates of small passerines in Europe. Low local survival rate of fledglings (0.050-0.055) probably reflects intensified emigration from this low quality area. Temporal variation in l was large (0.498-1.856). Despite of low adult survival and recruitment rates, the mean estimates of l (1.008 and 1.033) indicate an overall stability in the population size. Indeed, our results suggest that the immigration has an important role in the population dynamics of northern great tits. Thus the population is demographically and genetically dependent on core habitats which may cause adaptive problems due to intensive gene flow. Given those limitations, options for evolution of local adaptations in northern distribution margins are discussed.

Population differences in the structure and coloration of great tit contour feathers

“…Despite recent demographic studies suggesting that the northern population is a ‘sink’ (Karvonen et al ., ), Broggi et al . () showed that northern great tits locally adapt their winter metabolism.…”

“…Alternatively, birds from the southern population may be released from the selective pressure for high insulation capacity, and therefore grow an adequate plumage adapted to milder winter conditions. Despite recent demographic studies suggesting that the northern population is a 'sink' (Karvonen et al, 2012), Broggi et al (2005) showed that northern great tits locally adapt their winter metabolism. However, they appear to be unable to develop a highly insulative plumage structure in line with previous Feather structure data from the central and northern populations from Broggi et al (2011).…”

Northward expanding resident species benefit from warming winters through increased foraging rates and predator vigilance

“…It is, therefore, possible that cold temperatures limit success of great tits wintering in northern conditions by increasing mortality (Järvinen 1983 ). This conjecture is supported by an effect of winter temperature on annual survival (Perdeck et al 2000 ) and the lower survival of breeding great tits in the north (0.38; Karvonen et al 2012 ) compared to sympatric willow tits (0.59; Lampila et al 2006 ) but also compared to great tits breeding in Central and Southern Europe (ca. 0.5; Payevsky 2006 ).…”

Age structure in a newly established and increasing population: initially high proportion of young birds among nesting Great Grey Owls

“…The colonization of new areas by a bird species through natural expansion of the breeding range, from the arrival of the first individuals to the establishment of a population, is fundamental for our understanding of avian speciation and population ecology in general, and of the effects of human activities and climate change in particular (Newton 2003). Still, the mechanisms behind such expansions are poorly known, mainly because such events are rarely directly observed in detail (Karvonen et al 2012). These mechanisms may be intricate, as revealed for the cyclic replacement of one cavity nester by another in ephemeral habitat created by forest fire in Montana, USA; of the rapidly dispersing but poorly competitive Mountain Bluebird (Sialia currucoides) by the slowly dispersing but more competitive Western Bluebird (Sialia mexicana) (Duckworth and Badyaev 2007).…”