A population biology of breeding redshanks (Tringa totanus L.)
A breeding population of Redshanks was studied by trapping
adults at the nest and individually marking them, over a period of
nine years, on part of the extensive Ribble saltmarshes. Other
aspects of breeding biology were investigated over three years.
The capture-recapture analysis of the breeding adults
revealed an overall annual survival rate, of both sexes, of 0.77,
and a population of approximately 200 pairs in 1.04km?
Mate fidelity was very high, with 71% of surviving pairs
remaining faithful. Nest site fidelity was extremely strong for
faithful pairs and males with new mates, but significantly weaker
for females with new mates. A lower nest site fidelity of young
birds was regarded as a major contributing factor to their lower
The timing of both the onset and ending of the breeding
seasons varied greatly, and was determined mainly by the rainfall.
High rainfall delayed onset and hastened ending of breeding.
Mithin a breeding season the older birds bred throughout, while
the young ones were mostly not able to breed early.
The substantial losses of nests due to cattle grazing on
the marsh (45%) could easily be controlled by preventing the access
of cattle to the main breeding area until after the end of the
nesting season. Nest predation was rare (less than 4%) in most
years, but increased in a year of short vegetation (to 25%).
The production of pulli was estimated under varying environmental
influences and ranged from 0.73 to 2.28 pulli. pair":
The variation of egg size within the population was
investigated and the significant influences of laying order (within
a clutch) and maternal size demonstrated. Pullus size at hatching
was positively correlated with egg size and also with maternal size.
The growth and development of pulli were described for
weight, bill length, tarsus length and postnatal moult. For three
days after hatching the weight remained below the hatching value
and then rapidly increased, whereas the bill and tarsus showed a
linear increase in length
A tentative model of the population dynamics was produced,
despite the lack of good estimates of pre- and post-fledging
mortality. This model indicated a high pre-fledging mortality of
0.67 and also further highlighted the impact on the population of
cattle grazing during the nesting season.