Dispersal in an extensive continuous forest habitat: Marsh Tit Poecile palustris in the Białowieża National Park

Abstract

Dispersal is one of the least understood features in the life-history of organisms. Theoretical work concentrates on explaining dispersal of organisms in patchy and heterogeneous landscapes, but there are few predictions of dispersal patterns in stable, spatially extensive and largely homogenous landscapes, such as large forests. It is expected that we should observe short-distance dispersal in such places, that, to avoid competition with parents and siblings and incestuous mating, offspring should leave natal patches (natal dispersal), disperse independently in different directions, and move over distances that efficiently minimise the probability of meeting a sibling. Breeding dispersal should be very limited, site tenacity should prevail. To explore these ideas, I use observations of Marsh Tits Poecile palustris (a small passerine specialist of mature forests) made in the strictly protected part of the Białowie_ za National Park (Poland) over 21 years. The birds largely followed expectations: all fledglings left their natal territories and dispersed in different directions, and males moved shorter distances than females (median = 570 vs. 1,720 m). Apart from this difference, no influence of population density, fledgling time or family size was observed. No parent-offspring pairing occurred, with just one case of sibling-sibling pairing. After first breeding, individuals remained site-tenacious, as breeding dispersal distances were very short (median ca. 100 m). Such behaviour renders Marsh Tit poorly adapted to cross barriers and undertake long-distance movements, and this is actually observed in fragmented landscapes. Understanding dispersal patterns of organisms from extensive environments would be thus of value for basic and conservation science alike. IntroductionDispersal is one of the most important, yet least understood, features of ecology, population biology and evolution (Wiens 2001). Despite numerous efforts (e.g. three edited volumes during the last decade: Clobert et al. 2001Clobert et al. , 2012 Bullock et al. 2002), we are still a long way from comprehending the phenomenon, with Clobert et al. (2012) concluding that ''despite this interest and although the importance of this particular life-history trait is widely recognized, it is perhaps understudied with its overall importance in spatial ecology''. This is mostly a consequence of the enormous difficulties of gathering observations on the movements of individuals through the landscape. Theoretical predictions cannot be tested because the data required to verify them are impossible to collect.Hopefully, with the development of new tracking technologies (e.g. Koenig et al. 1996;Meyburg and Meyburg 2009;Stutchbury et al. 2009;Bächler et al. 2010), the impediment to data collection will be gradually removed. However, there seem to be additional, and conceptual, reasons hindering progress. Theoreticians tend to treat dispersal as a unique phenomenon that could be explained with a single set of rules, in the hope of a general theory of di...

Tits as bryologists: patterns of bryophyte use in nests of three species cohabiting a primeval forest

“…Data on the breeding tits were gathered in four sample plots of 33-54 ha within the Białowieża NP, spaced 1-2 km apart, and covering a total area of ca. 185 ha [their distribution is shown in Wesołowski (2015)]. The study was concentrated in three plots (C, M, and W) situated in oak-lime-hornbeam habitat composed mostly of hornbeam Carpinus betulus, lime Tilia cordata, pedunculate oak, spruce, and Norway maple.…”

“…Intensive searches for nests were made each spring, aimed at finding all breeding cavities of Marsh Tits in all the plots (details in Wesołowski 2002Wesołowski , 2015. Moreover, within the plots, all cavities known to have been used for breeding by birds in previous years, situated in living trees up to 5 m above the ground, were checked for the presence of active tit nests.…”

Offspring sex ratio of a woodland songbird is unrelated to habitat fragmentation

“…There are likely to be significant risks of starvation and/or predation associated with crossing the more open landscape matrix between woodland habitat patches. There is also no guarantee that even favourable routes such as hedgerows will lead to a vacant patch of suitable woodland in which to settle (Broughton et al 2010;Wesołowski 2015).…”

“…Czyż et al (2012) showed that the Marsh Tit population in Białowieża produced offspring with an unbiased sex ratio, reflecting the adult population in the breeding period. However, it is unknown whether the male bias in British populations of adult Marsh Tits results from a male-biased sex ratio among offspring or from differential mortality between full-grown birds, perhaps related to costs associated with female-biased dispersal in fragmented habitat (Broughton et al 2010;Wesołowski 2015). Under the environmental stress of a declining population in fragmented habitat (Broughton and Hinsley 2015) British females could be expected to manipulate their offspring towards daughters, which are rarer, more dispersive and less costly to produce, although manipulation towards males may produce offspring that are more competitively advantaged and able to settle successfully.…”

Understanding potential sources of bias and error in the biometric sexing of birds

“…The dispersal and settling ecology of Marsh Tits probably make localised founder effects quite unlikely in this species; juveniles invariably disperse out of their natal territories, and in small woods that support only a few pairs these young birds generally leave the wood completely, with any settlers tending to be immigrants that were hatched elsewhere (Broughton et al 2010, Wesołowski 2015). In the 13 ha Odd Quarter and 28 ha Upton Woods in Cambridgeshire, for example, which typically contained two and three breeding territories respectively, none of 88 colour-ringed nestlings subsequently bred in their natal wood, with all of the breeding recoveries (eight records) coming from other woods (pers.…”