Factors influencing Willow Tit Poecile montanus site occupancy: a comparison of abandoned and occupied woods

Abstract

The British Willow Tit Poecile montanus kleinschmidti underwent a decline of 85% between 1970 and 2003. The cause of this decline is unknown. However, several hypotheses have been put forward to account for it: competition from other tit species, predation by Great Spotted Woodpeckers Dendrocopos major and habitat change. In order to test these, woods that are currently occupied by Willow Tits were paired with woods (within 50 km) that had been abandoned by Willow Tits five or more years previously. Point counts for other tit species (potential competitors) and woodpecker species (potential predators) were carried out at ten evenly spaced points throughout each wood. Habitat variables were collected within a 50-m radius of where a Willow Tit was located (in the occupied woods) or where maps showed a Willow Tit had been located (for abandoned woods). No evidence was found for differences in numbers of potential competitor or potential predator species in abandoned and occupied woods. Soil water content was found to be higher at occupied sites. No other habitat features differed between the two categories of site. The drying up of British woods could therefore be implicated in the Willow Tit decline and this warrants further investigation.

Drivers of low breeding success in the Lesser Spotted WoodpeckerDendrocopos minorin England: testing hypotheses for the decline

“…It is clear that Great Spotted Woodpeckers are nest predators of the smaller species, as found in this and other studies (Wiktander et al 2001); however, this does not necessarily lead to a population-level effect. Other studies examining the impact of Great Spotted Woodpeckers on woodland birds have found little evidence of their impact (Newson et al 2010, Lewis et al 2007. However, it is plausible that other, more subtle effects that are hard to measure may have gone undetected in the present study.…”

“…Despite this increase there is little evidence for Great Spotted Woodpeckers being linked to population declines of other woodland species. For example, Lewis et al (2007) compared numbers of Great Spotted Woodpeckers in woods where Willow Tits Poecile montanus had persisted or gone extinct and found no significant differences. Charman et al (2010) found no relationships between wood occupancy by Lesser Spotted Woodpeckers and the abundance of Great Spotted Woodpeckers.…”

Anthropogenic activities influence the abandonment of Bearded Vulture (Gypaetus barbatus) territories in southern Africa

“…To address this issue, we used Caughley's (1994) declining population paradigm, postulating a series of plausible hypotheses and then testing which factors associated with these hypotheses were most closely linked to the abandonment of breeding territories. Similar approaches have been successful in elucidating important factors constraining other bird populations (e.g., Buchanan et al 2003, Lewis et al 2007, Amar et al 2011. In this study we explore the evidence for the following 3 a priori hypotheses: (1) territorial abandonment has been caused by anthropogenic activity, with abandonment occurring in areas with greater exposure to human impact; (2) territorial abandonment is the result of food shortages, with territories being abandoned in areas with insufficient food; and (3) territorial abandonment is being driven by climate change with abandonment occurring at nest locations most affected by climate change.…”

Factors influencing patch occupancy and within‐patch habitat use in an apparently stable population of Willow TitsPoecile montanus kleinschmidtiin Britain

“…Although there has been a rise in numbers of both these latter species in the UK in recent decades, Great Tits +82%; Eaton et al . 2007), there is little evidence to support this hypothesis as a driver of the national Willow Tit decline (Siriwardena 2004, Lewis et al . 2007).…”

“…Three possible causes of the Willow Tit population decline have previously been investigated: competition with other tit species, predation, and changes in habitat quality (Siriwardena 2004, Lewis et al . 2007).…”