BTO: Coot disperse to start breeding
The numbers of coot on the local gravel pits have dropped, a sure sign that winter is at an end and that the birds have dispersed to begin the first of their two or three breeding attempts of the year.
Those that remain, a dozen or so pairs scattered across the pits, have already started to construct their rather simple nests. Each nest is built from the bottom up, supported on the partially submerged branches of bankside trees that trail into the water, and constructed from the leaves and stems of aquatic vegetation.
Over recent days these platforms of plant material have grown in size and many of the nests are near to completion, with just the nest cup left to form.
The nests seem rather exposed, the trees yet to leaf, and you would imagine that the levels of nest predation would be high. Otters have access to many of the pits and a brooding coot or its young would make a suitable meal. At present, with no nest contents to defend, the adult coots simply loiter on the water and cluck their disapproval with a sharp sounding click. However, it is worth noting that coots are aggressive birds and may target this aggression towards potential nest predators as well as to rivals and other species.
It will not be until the end of the month that the first eggs will be laid and I will have contents to record for the British Trust for Ornithology’s (BTO) Nest Record Scheme (www.bto.org/nrs). The chicks that hatch from the clutch of 5-8 eggs will leave the nest platform to join the parents on the water fairly soon after hatching, perhaps returning to the platform to roost overnight. The parents divide the brood into two and each adult is responsible for looking after certain chicks, providing them with food until they can feed independently. The young may not become fully independent for a couple of months and it will only be after this that the pair can think about making another breeding attempt.
Coot populations have fared well over the longer term, with populations more than doubling since the late 1960s. The last few years, however, appear to have been less kind and a 14 per cent decline in their UK breeding population has been charted since 2002. While the change in fortunes may be linked to a decline in food availability during the breeding season, coot populations are also known to be sensitive to poor winter weather. At least the relatively mild weather of the winter just ended should have delivered a healthy population through into the breeding season.
The nests of these smart birds are relatively easy to find and to monitor, just the sort of species that might tempt you to get involved in nest monitoring for the BTO.