What are these harriers up to?
Over the last ten years or so, the first egg of the first clutch on the UU estate has usually been laid around the beginning of the second week of April. Last year the first egg was laid on the 13 April, with many other clutches starting around the 16 – 18 April. So far, nothing, despite the relatively pleasant weather over the last couple of weeks. However, anytime soon…
Why should this be? One theory could be that the numbers of voles have fallen over the winter, meaning fewer about come spring. Because of this, the harriers have had to wait for the arrival of one of their other main food resources, meadow pipits, which spend the autumn and winter elsewhere (unlike the voles) before they have been able to start the breeding season. This idea could be supported by the fact that there have been very few, if any, sightings of short-eared owls, which feed almost exclusively on voles.
In terms of overall numbers, the situation seems to be very fluid at the minute; though there might be seven occupied nest sites so far.
As mentioned in the last update, we had the first guided walk of the season on the 6 April. Overcast but dry conditions meant a pleasant few hours for the 16 participants, with seven species of bird of prey seen: hen harrier, buzzard, peregrine, merlin, kestrel, sparrowhawk and osprey! The osprey was of special note for me, as, despite a regular passage of birds through the estate during the spring, this is the first for me in Bowland. All that was missing was a red kite, which turned up a week late, last Monday.
Next update should announce the first confirmed hen harrier nesting attempt.
Could be because first year males have the same plumage as females, until they start to moult in the summer of their second calender year and gain the striking adult male plumage. The difference is so striking that, in old literature, it was actually believed that males and females were two different species. Might also be because males have a slightly lower survival rate than females. Hen harriers are regularly polygamuous, with males paired with more than one female.