Second broods don’t occur every year and usually depend on the food available so it’s the vole population that determines whether the owls will lay again.
Normally; a female will do her annual wing feather moult when she’s inactive, sitting on eggs in April/May and I usually find the remains of the discarded feathers during my early inspection in May/June. Finding these feathers usually tells me that this pair won’t 2nd brood. However, if the female doesn’t moult, it can mean that they will 2nd brood but how do they know in April what the food supply will be in August??
It beats me but all I know is that after ringing 78 chicks from 30 pairs in the first round; about 2.5 chicks per pair which is low; I commenced another round of checking my early breeding birds and have found up to now 10 pairs on new eggs and they’re laying more eggs this time than they did in April with 47 eggs including 2 sevens and 3 sixes. This week I found the pair in the water tank had laid 6 eggs after their 2 chicks had fledged and it will be into November by the time they get ringed!! Not that I’ve got too many expectations as to how many of these late fledging chicks will survive. Winter mortality rates are high; young Barn Owls are taught to hunt by the parents soon after fledging and then have to go off to fend for themselves. While birds fledging in August have 3 month’s experience before the onset of winter, these young birds could be into bad weather almost as soon as they fledge so I fear that very few will survive to breed next year.
There’s still a number of other breeding boxes to check so there’s likely to be quite a few more; I’m not complaining but it’s gonna be a long season!!