Eggs!

Posted 2nd Apr 2015 | Comments (0) |

Peregrine sitting on the eggs
Peregrine sitting on the eggs

As the weather warms, wildlife watchers are on the lookout for hatchlings, with many people now avidly viewing their own nest box cams. The Nottingham Trent University peregrine falcon’s eggs are here, having come quite early in March. The 1st egg arrived on the joint earliest date recorded for the Nottingham nest in recent years, but it wasn’t the earliest known peregrine egg this year – that honour went to a pair in London. Eager viewers of the live web cam feed were the first to spot the eggs being laid.

The female lays her eggs over a few days and doesn’t usually begin to incubate them until the last egg is laid. This is to ensure hatching happens relatively synchronously, a survival technique that gives the young an equal chance of survival, spreading the odds over a number of birds. This technique is practiced by most birds, but some, like the tawny owl and jackdaw, incubate after the first egg. This causes the eggs to hatch asynchronously, meaning one chick is less developed than the others. The adult then decides if the environment is right and if there is sufficient food to feed the last chick.

To keep their eggs warm, peregrines, like many other species have evolved a special adaptation – a featherless area on their breast called a brood patch. In this area the skin becomes thicker and there is an increased blood flow to help transfer body heat from the adult bird to the embryos inside the eggs. The more regular viewers amongst you might even have seen the female lightly plucking her brood patch to expose more skin to help her keep the eggs warm. Feathers that are dropped or plucked help provide further insulation and protection.

It’s not unusual for adult birds to leave the nest and studies show this has little effect on hatching success. The NTU peregrines are normally fairly diligent and dedicated, but the fact is, it’s unknown if this year’s pair are the same birds. The site has been in use for over 13 years, so it’s highly likely that the birds are different to previous years. As the adults aren’t ringed, it’s difficult to tell for sure.

Whilst the eggs are being incubated a developing peregrine chick has its head tucked under its wing, waiting to hatch. Chicks also have a large muscle called ‘the hatching muscle’, which runs from the middle of the neck right to the top of their heads.  When the eggs have been incubated for about 30 days this muscle starts to contract. This makes the chick's head snap upward and the egg tooth, a hard pointed area on the top of the beak, comes into contact with the eggshell, causing it to crack.

A day or two after making the initial hole in the shell, known as a ‘pip’, the chick starts to move around inside the egg. As the chicks turns around the egg tooth presses against the inside of the shell, eventually cutting a line right the way around. Once this is complete the chick is able to break out.

In the meantime, it’s a waiting game for those on the lookout for young spring chicks and a lot of patient eyes will be on the peregrine cams.

To view the peregrine cameras live, please visit www.nottinghamshirewildlife.org and then click on the peregrine story on the home page.

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