With 10 pairs of chough having started nest building by end of the first week of April we began checking on these sites today for signs that clutches had been laid and incubation was underway. The female carries out all the incubation duties but only begins once a full clutch is laid (up to 6-7 eggs usually). The male bird feeds her during this time so once you start seeing single birds busily feeding in our sheep grazed fields you start to suspect they are under starters orders.

We have checked 5 of the 10 sites and of these 2 are definitely incubating, 1 is possibly incubating but more likely still in the process of laying the full clutch, and 2 are still taking nesting material in indicating they aren't quite ready yet

Most pairs will begin to incubate from mid to late April so it could be a couple of weeks yet before all birds have laid and settled into the new routine. As we can't see the actual nest we have to make our judgement based on visual observation of the birds. The usual routine is the male bird returns calling, he either goes into the nest site and tempts the female out or sits outside the nest site calling until she relents and comes out for a feed (some females refuse to budge and the male presumably feeds her on the nest itself!). With both birds outside the nest site the female noisily begs to the male and he regurgitates food (mainly soil invertebrates) from his crop directly to her. A period of mutual preening usually follows then the female will return to the nest site and the male flies off to begin foraging for the next meal.

All pairs are slightly different - some males come back noisily, announcing their presence to all and sundry, while others swoop into the nest site silently (and quite possibly cause the female to jump out of her skin!), some females site tight on the nest and refuse to come out, others feed at the nest entrance, while others fly away together and leave the nest site unattended for up to 20 minutes. Some males forage directly outside the nest site while others head inland and feed in the fields. Some males bring the female off the nest up to 4 times an hour to feed her while others return once an hour at most.

Whatever strategy pairs adopt they often maintain it throughout the incubation period and even from year to year if they stay with the same partner at the same site. When we had colour ringed birds in our breeding population it was clear that more experienced birds tended to adopt a more relaxed attitude whereas the younger pairs were the ones that kept returning frequently to the site, perhaps 'worried' they would lose their females and/or nest sites if they were away too long.

To confuse matters young, non breeding pairs can build 'dummy nests' at this time of year. Today I saw a pair flying around with beak fulls of dried grass landing on cliff faces and checking out random holes. They were too near an established site though and the male bird came over at speed and told them to clear off! All part of the learning process and while it's possible this might turn out to be a late 11th pair, they were more likely to be practising for next year

We'll keep checking the sites over the coming 2 weeks and by the end of the month can hopefully report back on how many of the 10 nest building pairs went on to lay eggs. I'm hoping for full marks 10/10!

The video below was from this morning and shows a pair who have not yet laid a full clutch and are spending hours each day furiously feeding, particularly the female who is busy produces all those precious eggs