Recruitment patterns of Blackbirds (Turdus merula) in urban fragmented populations

The purpose of this paper is to study the effects of habitat fragmentation on Blackbird Turdus merula recruitment in 21 urban parks in the city of Madrid (Spain) during two consecutive breeding seasons (1997-98). We found that: (1) recruitment did not vary between years, showing high levels of spatial and temporal constancy; (2) recruitment was not affected by Blackbird density either within or among years; (3) fragment size accounted for a significant proportion of the variance of Blackbird recruitment; (4) after controlling for area effects, shrub cover in 1997 and shrub height in 1998 explained the remaining proportion of the variance of Blackbird recruitment; (5) human disturbance (rate of visitors and traffic load) and predator density (Magpie Pica pica and domestic cats) did not exert any significant influence on recruitment. Fragment size could be considered as the main indicator of the quantity of available habitat for reproduction, also decreasing human interference from park fringes and the levels of nest predation, whereas shrub cover and height could be regarded as factors of habitat quality, increasing the availability of nesting substrate and cover to rear and protect offspring.

Fernandez-Juricic, E. & Telleria, J. L., Ardeola 46(1), 1999, 61-70