Natural History Wanderings

Cuckoos are known for laying their eggs in the nests of other birds and getting the other birds to raise the young cuckoos often at the expense of their own young. Scientists recently decided to study why some Magpies were successfully targeted by cuckoos yet others found ways to avoid them having their nests parasitized. They found that successful strategies varied depending on whether the Magpies were early or late breeders. The study found

The ones who were most successful built large nests early in their breeding season. Early in the season the trees are bare and all nests are easily visible to cuckoos. During this time smaller nests have fewer sticks in their roofs and more entrances, making them more accessible and more likely to be targeted. So, magpies with larger, less-accessible, nests are more likely to escape parasitism.

But later in the breeding season it is the magpies who build small nests who evade cuckoos. This may be because trees become leafier and smaller nests are more easily hidden, so magpies that build small nests and conceal them in wooded areas are less likely to find a cuckoo moving in.

Read more at Planet Earth Online A magpie’s guide to avoiding cuckoo parasitism.