Brood Patches and Expected Hatch Dates
The female falcon just before an incubation exchange occurs.
The female falcon has finished with egg laying and the pair has moved onto the incubation phase of the nesting season. The fourth and final egg was laid on March 29th but because true incubation typically begins when the second to last egg is laid, we would count March 27th as the start of incubation for the current clutch.
Incubation also means that Falcon Fans are just about guaranteed to see one of the adults on camera at all times as the eggs are generally not left unattended for extended periods of time during incubation exchanges. Both the male and the female take shifts incubating and thus have developed paired brood patches (featherless patches of skin on the bird’s breast which aid in incubation). By selectively losing these feathers, more direct contact area is created with the skin of the adult bird’s breast and thus the numerous warm blood vessels which are used to maintain the eggs temperature. Although the brood patches are obscured by an outer layer of feathers and therefore not visible to Cam watchers, you may observe the incubating bird shifting its position or shimmying atop the eggs. These movements allow the bird to better position the eggs to ensure maximum contact with their brood patches.
The male gingerly adjusts his placement atop the eggs to ensure contact with the brood patches.
Peregrine falcon eggs are incubated for roughly 33-35 days which means we should expect to see our first signs of hatching around April 29th-May 1st. As a reminder, last year we observed two eggs pipping (one of the early stages of hatching) 34 days after the penultimate egg was laid. So if you are hoping to catch the hatching process as it unfolds, be sure to mark those calendars now!