Peregrines @ Rijksmuseum - new clutch

Urban refugees

A neighbour destroyed their nest just before any eggs were laid. But those eggs were coming and the couple found refuge on our balcony. No time to build a nest. Around here, if not disturbed, exposed eggs like these usually get predated by Magpie Pica pica or Carrion crow Corvus corone.

Failure...

Two-egg clutch of Barn Owls (Tyto alba guttata) in a wall mounted nest box located in a green suburb of Zwolle, The Netherlands. An infrared camera connection showed that one of the two breeding birds disappeared during early egg-stage (halfway April), but the true cause of failure remains unknown. The box was installed over 20 years ago and became occupied by a single Barn Owl pretty much every winter and occasionally in summer. During summer 2015 a second bird appeared and a first breeding attempt was made the following year, which also failed during early egg stage. Today the box got cleaned out, the eggs were removed and 85 pellets were collected and will be used to identify prey items.

Variation on the egg-theme.

When searching for bird nests, occasionally one can find an egg that does not look like one at all. Deformation of an egg can occur for a variety of reasons (which I will not discuss here) and can result in some strange shapes. The weirdest egg I ever observed had been laid by a Black-legged Kittiwake Rissa tridactyla in its nest on the large former radar tower on Middleton Island during the summer of 2010. I have no idea what would be the cause of its remarkable shape. 

Deformed Black-legged Kittiwake Rissa tridactyla egg found on Middleton Island in the summer of 2010 (T. van Nus)

Unfortunately, I only have these two photos to show and can’t retrieve any background information about the bird that laid it, though it possibly had been a bird that was included in some physiological study…