March 2019 Nuthatches are great engineers watch out for them.

The new breeding season will shortly begin and one of the things I love to watch out for are the local Nuthatches when they start to build their nests.  They habitually find a hole in a tree and then proceed to modify the size and shape so that they can just fit through.  They do this by bringing in wet mud and plastering this into the hole. They build this up letting it dry like cement.  Nesting sites in hollow trees are always at a premium, and having this ability obviously gives them greater opportunities.
In the first picture the Nuthatch begins bringing in mud to complete the transformation

Great site but predators could get in!

It takes a lot of effort but the resulting cavity, when finished, is a lot more secure for raising their vulnerable chicks.

Now the hole is just the required size

  Spring is a great time of the year and this is another interesting thing to look out for as the breeding season gets underway.