Territory and Breeding Density in the Great Tit, Parus Major L.

Abstract

This paper describes an investigation into whether or not spring territorial behavior was limiting the breeding density of a population of Great Tits on Wytham Estate, near Oxford. The analysis of distances between neighboring nests showed that nest sites were more spaced out than would be expected from a random distribution; this indicated that interactions between the birds produced at least a local density—limiting effect. In 2 successive years, established territorial pairs were removed from a stable spring population in mixed woodland. The removed birds were rapidly replaced by new pairs. These newcomers were largely first—year birds; they came from territories in the hedgerows that surrounded the wood; the vacated hedgerow territories were not refilled. The hedgerows were found to be suboptimal in terms of reproductive success. Thus territory limited the breeding density in the optimal habitat. Song advertisement is probably important in maintaining territorial boundaries, hedgerow birds being able to detect the presence of individual woodland territory holders by recognizing their songs. The effect of winter food supply on the population was investigated by supplying excess food throughout one winter. This artificial food supplement appeared to have no effect on the number of Great Tits breeding in the wood, but did produce an increase in the case of a related species, the Blue Tit. The results show that territorial behavior influences density; this is not considered to be a function of territory in the evolutionary sense, but rather a consequence of spacing out that has been selected for in some other context. A possible advantage of spacing out in the Great Tit is as a defense against predators. Territory size varies considerably from year to year. These variations are the result of interactions between the birds themselves, rather than direct adjustments of territory size to fluctuations in some environmental resource. Even though territory has an effect on the number of birds breeding in the wood,it is not an important density—dependent factor acting to regulate the population.

The Significance of Variations in Body Weight and Wing Length in the Great Tit, Parus Major

“…A short experiment reported by Dhondt (1971) also indicated that supplementary feeding in winter can increase the breeding density. On the other hand, Krebs (1971) found food supplementation in the winter to have no effect on the size of the breeding population. However, his results are not conclusive because his experiment lasted only one winter, wich happened to coincide with a good beechmast crop.…”

Slow to change? Individual fidelity to three-dimensional foraging habitats in southern elephant seals, Mirounga leonina

“…Augé, Chilvers, Moore, & Davis, 2014; Weber et al, 2015), even when habitat quality is 3 sub-optimal (Krebs, 1971;Merkle, Cherry, & Fortin, 2015). Fidelity to foraging areas may 4 have long-term advantages for individual fitness, particularly in unpredictable environments 5 (Switzer, 1993).…”

Space Use of Adult Spanish Imperial EaglesAquila adalberti

“…The territory, or defended section of the home range, can be described in terms of two main factors: nesting requirements and food resources, with territory size varying in relation to the environment so as to maximize the fitness of the individual (Patterson 1980). Thus, territory size can be viewed in terms of two competing hypotheses: as a response to resource density (food availability), so that the territory contains enough food to satisfy energetic requirements (Schoener 1968, Gill & Wolf 1975; or as a response to defense costs, where the variation in territory size occurs because more competitors are attracted to areas rich in resources, and such areas are, therefore, more costly to defend per unit area (Krebs 1971). The analysis of home range is based on the utilization density of the range, and is defined as the minimum area in which an animal has a given probability (for example of 95%) of being found (Worton 1995).…”