The young of a clutch hatch over two or three days and are brooded until their feathers develop and eyes open five days after hatching.
It is possible that once the first-laid eggs of a clutch hatch, females reduce time spent incubating, so that they can feed the newly hatched nestlings [44].
Males were removed when an egg sac was observed, and females moved to fresh plates as each successive clutch hatched.
On brood-day 11 or 12 (brood-day 0 is the day the first egg of a clutch hatches), we ringed nestlings with a numbered aluminium band, weighed them on an electronic balance (Acculab, Pocket Pro 250-B) to the nearest 0.1 g, and measured their right tarsus length with dial callipers to the nearest 0.1 mm.
However, an indication that early incubation intensity and EPP covary comes from our previous study on blue tits (Vedder et al. 2010), because females whose clutch hatched more asynchronously after adding model eggs prior to the start of laying, also had a lower proportion of EPO in their nest.
In addition, there is extensive information regarding life history traits such as breeding attempts, first egg date, egg mass, clutch size, hatching date, hatching success, fledging success, fledging size and recruitment success for those birds that recruit to the breeding population (see, for example, McCleery et al. [ 20] and references therein).
As part of a long-term study on this species we monitored over 16,000 Nazca booby nests at Punta Cevallos, Isla Española, (89° 37' W, 1° 23' S) in the Galápagos Islands since 1984 in which laying dates, laying order, clutch size, hatching dates, and hatching order were recorded.
The breeding traits studied were laying date, clutch size, hatching success, fledgling success and breeding success.
This makes it seem likely that the tests were containers, to protect whatever was inside - whether that was a "hibernating" or encysted organism, or a clutch of hatching eggs.
To control for maternal effects through egg size [30] we measured 10 30 eggs from each clutch before hatching.
