Dr Phil Shaw* (University of St. Andrews), Prof Derek Pomeroy (Makerere University), Jane Yatuha (MSc student 2003-4), David Ebbutt (2004). Field support staff: Narsensius Owoyesigire and Savio Ngabirano (ITFC)
Funding sources: WCS, British Ornithologists’ Union, African Bird Club Conservation Fund
Project dates/duration: The project was established in 1995, and is ongoing.
Nestbox 21
Background:
Much of our understanding of evolution comes from the study of life-history theory – how animals invest differently in each stage of their life cycle, so as to maximise their lifetime reproductive output. Many songbird species in Europe and North America achieve this by rearing one or a few large broods in the course of their relatively short lifespan. In contrast, most tropical and south temperate songbirds appear to be long-lived ‘slow’ breeders, in the sense that they lay small clutches, have longer breeding cycles, and may suffer higher levels of nest predation. Theoretically, this type of life history may render their populations less resilient; less able to increase quickly if or when the opportunity arises.
Tropical and south temperate species account for about 80% of the world’s songbirds, yet most of what we know of songbird life histories has been drawn from long-term studies of north temperate species. The tits and chickadees (Paridae) exemplify this disparity.
While species such as the Great Tit Parus major, Blue Tit Cyanistes caeruleus and Black-capped ChickadeePoecile atricapillus are among the world’s most intensively studied birds, much less is known of the 15 tit species endemic to sub-Saharan Africa.
The aim of this long-term study is to examine the ecology and life history of the Stripe-breasted Tit Parus fasciiventer, a small songbird endemic to the Albertine Rift. Specifically, we aim to determine why the species is so much less abundant than its north temperate relatives; how it times its breeding activity in relation to weather patterns and food availability; why it rears so few chicks (typically just 2-3) at each breeding attempt; why some adults choose to help their parents, rather than find a mate; and whether the species’ ‘slow’ breeding behaviour is indeed balanced by a longer lifespan.
There are several likely explanations for the Stripe-breasted Tit’s low breeding output: brood sizes may be more tightly constrained by competition for food; nest predation rates may be higher (encouraging females to avoid placing too many eggs in one ‘basket’); or adults may be ‘unwilling’ to risk their own survival and future breeding opportunities by attempting to rear large broods of chicks.
Approach
In 1995 C. Perrins (Oxford University) and D. Pomeroy (Makerere University) erected 30 nestboxes in the vicinity of the ITFC field station at Ruhija. A further 30 boxes were later added. Each month, all boxes are inspected for signs of Stripe-breasted Tit breeding activity. For each nest, we aim to record laying dates, clutch size, hatching dates and fledging success; time spent incubating; food delivery rates by each adult; and nestling growth rates. In addition, colour rings (bands) are applied to all nestlings and their parents, to help track their subsequent movements and survival.