Blog: Owl Box LIVE – Egg laying to Hatching

By Inca Johnson, GWCT Farmland Ecology Placement Student

Over the last few months, we have been eagerly watching the activity of the nesting pair of barn owls on Owl Box LIVE. Earlier in the season we captured evidence that the pair were breeding and subsequently the female laid four eggs.

She has been incubating these eggs since the middle of April, and so far, two chicks have hatched which are being fed small pieces of prey until they are large enough to swallow prey whole. The male is bringing the majority of this food to the nest as the female is still incubating the unhatched eggs, but we are expecting further chicks to hatch any day now!

When does the Barn Owl breeding season commence?

Barn owls can begin breeding within their first year, with nesting and subsequent egg laying most commonly occurring within the spring and summer months. They have been known to nest throughout all months of the year, but favour March to August as there is more food available and the warmer weather improves their chances of rearing a successful brood. This long breeding season allows some experienced breeding pairs to have two broods per year, with second clutches normally laid in July.

Typical clutch size

Barn owls can lay between 3 and 11, and an average of 4.7, eggs per brood, although breeding performance can vary annually depending on prey availability. Experienced breeding pairs with a good food supply typically breed earlier in the year than first-year birds, with these clutches being larger in size, on average, than those later in the year when food becomes scarcer.

The Owl Box Initiative team have been out monitoring barn owl nest boxes this month with a GoPro camera mounted on a pole to minimise disturbance. We found this owl on a clutch of eggs with a hatched chick, and will be checking the box again in June to see how the chicks have progressed.

Egg laying and incubation

Owl Box LIVE Footage: Female adjusting eggs for incubation

Female barn owls begin incubating once the first egg has been laid, with additional eggs laid over an 8-to-21-day period. Incubation continues for 30-to-32 days for each egg, until the last egg from the clutch is hatched. This leads to asynchronous hatching, where eggs from a clutch begin to hatch every 2-to-3 days, usually in the order they were laid. Asynchronous hatching creates an age difference within the clutch, so owlets are at varying stages of development. This helps to minimise a peak in food demand by extending it over a longer period, allowing the breeding pair to provide enough food for all owlets, which increases the entire clutch’s chance of survival.

Come on over to our new website – www.owlboxinititiative.com - to find out more about the project, and to our Owl Box LIVE page to view the breeding pair of barn owls in one of our project nest boxes!