Male Crossbill feeding young, by Andrew Dixon
Crossbills | MONITORING
The male will feed the chicks for the first 10 days and after this period both parents will search for food. Chicks excrete over the rim of the nest, and the nest rim becomes stained white.
A Crossbill season in Devon In this article, Mark Lawrence outlines the fieldwork he carried out with Marcus Betteridge, Paul Haffield, Josh Marshall, Mark Penney and Jim Shortridge during the 2019 Crossbill breeding season, when the Sitka Spruce was masting in South Devon. Their sample of nests found may shine some light on the complexities of the Crossbill’s breeding season and the importance of timing, weather and availability of conifer seeds within these forests. As a nest recorder, in the depths of winter
I yearn for the coming breeding season and eagerly look forward to the spring and all the early-nesting birds that will surely follow. Walking the coastal paths in midFebruary, searching for that early Raven; visiting those old familiar sites, their secrets unveiled many years ago, scanning the cliff and finding that old friend with its new mass of sticks is a rewarding sight. Whether your first nest of the season is a Raven or maybe a Stock Dove, Tawny Owl, Robin, Blackbird, Grey Heron or Coot, one thing is guaranteed – every year you will be able to go out and find their nests in the same old spots; old holes, ponds, bramble or hedges. But there is one species that does not give you this guarantee. Many years could pass before they breed again in their chosen habitats. Only when certain conditions are favourable will they attempt to breed, so every year we enter these habitats hoping that nature’s chemistry will provide the ideal environment for the Common Crossbill.
FOOD AVAILABILITY
The Crossbill is a nomadic species and opportunistic breeder. It will search widely Winter 2020
for a forest that holds a good food source and will breed when that food source becomes available. Crossbills feed mainly on conifer seeds, but different species produce cones at different times of the year, so depending on what species of tree is producing cones, the Crossbill can nest in any month. Scots Pine open later than spruce, providing a food supply lasting into July, bridging the gap between successful spruce crops and sometimes allowing the Crossbill to breed into May or June. Larch cones form in May and open from late summer; in years of good crops this allows Crossbills to breed into September or October (Newton, 1972). Sitka Spruce masts in periods of between one and six years, and studies suggest coning in Britain is episodic with one mast year (occasionally two) followed by a period of poor cone production, in some cases lasting four years. Masting and synchrony of coning over large areas are thought to be evolved strategies. Numbers of seed-eaters are thought to fluctuate in response to food availability with the seed-eaters becoming satiated in mast years and never reaching high enough densities to consume all of
THANKS We would like to thank the Forestry Commission for allowing us access to Haldon forest to conduct this survey.
LIFECYCLE – 17
