The time for egg hatching is fast approaching, and our Osprey pair have been patiently attending to their three eggs in their own remarkable way. However, incubation must be complete before the chicks arrive, and we know some of you will be itching to learn more about how this process actually works…

Incubation is the period where the chick embryo develops within the egg; in Ospreys this period begins as soon as the first egg is laid.

Using their brood patches – areas of bare skin, dense with blood vessels – both the male and female transfer their body heat to the eggs (Poole, 1989). Consistent temperatures are required for the embryo development and their patches help the parents do an efficient job. We often see LF15 or LM12 wiggling into the bowl of the nest, and while we may joke with visitors by calling them “fussy”, this is actually the Ospreys’ way of ensuring the eggs are in contact with their patches and are being properly incubated.

While our chicks are growing within the safety of their eggs, gasses such as oxygen and carbon dioxide transfer in and out of the egg with help of the shells’ porous structure (Hanzák, 1973). This is necessary for the development of chicks and allows them to grow as much as possible within the egg before hatching.

The duration of incubation varies by species, lasting anywhere between 11 days for some of the smallest passerines, to 80 days for large birds such as the Albatross (Rahn & Ar, 1974). For our Ospreys incubation is on average 37 days, and as of today – 17th May – we are on day 34!

Now that we are nearing the end of the incubation process everyone at the reserve is getting more excited about when the eggs will hatch. Stay posted for more information on the egg hatching process… and the telltale signs that it’s about to begin!

Jennifer – Species Protection officer

Did you know? – The gender of birds is genetically fixed during egg fertilisation, however for some reptiles, the gender is determined by the temperature at which the eggs are incubated (Pen et al. 2010).

Hanzák, J. (1973) Birds’ Eggs and Nests. Hamlyn Publishing Group

Pen, I., Uller, T., Feldmeyer, B., Harts, A., While, G.M., & Wapstra, E. (2010) Climate-driven population divergence in sex-determining systems. Nature. 468, pages 436–438.

Poole, Alan. F. (1989) Ospreys: A Natural and Unnatural History. Cambridge University Press.

Rahn, H., & Ar, A. (1974). The Avian Egg: Incubation Time and Water Loss. The Condor, 76(2), 147-152. doi:10.2307/1366724