The other weekend I was treated to a very special sight. I’d been lucky enough to go out into the forest with a couple of nest recorders, specially trained and licensed individuals who monitor bird nests for the British Trust for Ornithology (BTO). Nest recording is an extremely important component of the BTO’s work, providing information on those changes in breeding success that might result in population decline or flag up the worrying effects of human activities. It was nest recording that highlighted the impact of organochlorine pesticides on the breeding success of birds of prey like Sparrowhawk and Peregrine.
As well as helping to locate nesting birds, I was taken to see two rather special nests, both of species whose nests I had never seen before. The two species were Siskin and Crossbill, both of which are very early nesters and their breeding attempts were now well advanced. There seem to be very good numbers of both species in the forest this year. Crossbill numbers in particular tend to rise and fall, with increased numbers breeding here in years when we have had a good influx of birds from Scandinavia during the previous winter. We were certainly treated to excellent views of both species as they fed, perched and called in the firs.
Although Crossbills are fairly ‘tame’ when nest building and appear to disregard the observer, they are rather furtive when they have eggs or young in the nest. Visits to the nest to feed are rather infrequent and the birds are very careful in their approach. The nest itself is also rather hard to spot, placed on a branch high in a conifer. We had to strain our necks to spot where the nest was located, the slight bulge of material silhouetted above the branch on which it was placed. The same was true for the Siskin nest which, though placed lower down in this instance, was rather more compact. We managed to get a good view of the Siskin nest from slightly below the horizontal, standing well back but using our telescope to good effect.
Conditions must be difficult for these birds, nesting so early in the season, and even though the day of our visit was a warm and sunny one, there were still the remnants of the gusty winds that had been present over previous days. One of the Crossbill nests that we went to check on had been blown down by the wind, a small amount of debris left in the tree, with nest and eggshell remains scattered across the forest floor. There was a good chance that the birds from this failed attempt would have another go so all was not lost for them.