A World of Nests

Gannet Colony - Saltee Islands, Wexford. Many seabirds nest on steep cliff faces.
Text by Eric Dempsey.
Pictures by Joe Curtis and Eric Dempsey

Spring has at last arrived and all around us our resident birds are busy proclaiming their territories and selecting suitable nest sites. Already, many of our summer visitors are reaching our shores and shortly they too will be nest building. But what are nests? Put simply, nests are where birds lay their eggs, incubate those eggs and, for many species, where the chicks remain until they are fledged (ready to leave the
Swallows build nests of mud, lined with feathers...however it can be a tight squeeze when the chicks get old.
nest). Most people, if asked what a nest was, would describe a cup-shaped object made of grasses wedged in between branches in a tree. Such a description would be right. many birds do build nests exactly like that. However, as there are many species of birds, there are equally a vast array of nest designs and nesting places. In fact there are some birds that don't even bother to build nests at all! It is also important to remember that nests are a purely summer residence for birds.once the breeding season is over, they are no longer required and are abandoned. Nests vary from highly elaborate and beautiful constructions like those of Long-tailed Tits to simple hollows scraped in ground like those of Ringed Plovers.

Ringed Plovers - many species like Ringed Plovers don't build nests at all...they simply scrape a hollow in the ground and lay their eggs in it.
Ground Nesters
Many birds choose to nest on the ground and employ many different strategies for nesting. Some birds like Guillemots and Razorbills simply lay their eggs on the ledges of the steepest cliffs. There is no attempt to even pretend to build a nest. The eggs are pointed and oval shaped so that, if a parent bird should knock against it when leaving the ledge, the egg will simply roll in on itself in a tight circle.if it were more rounded,
Greater Black-backed Gull chick - the chicks and eggs of many ground nesting species rely on camoflage for protection.
it might roll off the edge! Other seabirds like Gannets nest on similar steep cliffs but do construct a large cup-shaped nest of seaweed and other coastal material... including discarded fishing netting. These birds rely on the fact that their nests are on such steep cliffs for protection. Potential predators simply can't reach them. Many birds of prey like Kestrels and Peregrine Falcons also nest on ledges of cliffs and, in some cities, on high-rise buildings. They can build quite large nests of twigs, grasses and straw but in some cases, Kestrels will also use old crow nests or even nest in large, open nest-boxes. These boxes can be erected where there are no other suitable locations.

Long-tailed Tits build ellaborate, domed nests made with lichen, moss and spiders webs
Other birds that nest on the ground tend to rely on camouflage to protect their nest location. Many ground nesting birds like Little Terns, Ringed Plovers and Skylarks sit tight on the nest and simply blend into their surroundings. When they leave the nest, their eggs and chicks are also perfectly camouflaged. Other ground nesting birds like gulls also rely on camouflage with their patterned eggs and chicks making them almost impossible to see. One ground nesting duck, the Eider, lines the nest with her dense down feathers... one of the warmest naturally produced substances in the world. Swans also nest on the ground and build large nests of weed and feathers. Like all wildfowl (ducks, geese and swans), the chicks are hatched with down feathers (most chicks are hatched bald). Within a day, the nest is abandoned and all the chicks take to the water with their parents.

Eider - the female Eider Duck lines her nest with down feathers plucked from her breast - the warmest naturally produced insulation in the world.
Cup-shape Nesters
Many species prefer to nest off the ground and in the relative safety of trees. At least here, ground predators can not reach the eggs or chicks.although there are always others to rob the eggs. Many of these birds build more complicated nests than the ground nesters. Many construct cup-shaped nests made of grasses, straw and even dung. Many species like the Blackbird will also use to mud to strengthen the construction. Once the main frame of the nest is complete, the birds will then line the nest with feathers, animal hair and grasses. At the point where the nest is almost complete, the female (who in many cases does most of the incubation), will frequently sit deep into the nest and move her body to ensure that the inner nest in comfortable and fits perfectly to her body size. When sitting on the eggs, she needs to make sure that the eggs are not exposed to any cold. Cup-shaped nests also make perfect sense...
Wrens also build covered nests, often hidden in ivy or under the beams in old sheds.
they are usually deep enough for the parent to sit and incubate the eggs comfortably and when the chicks emerge, they are too deep for them to fall out. If a tree-nesting chick falls from the nest, they are usually doomed... there is no way for them to climb back in! Another cup-shaped nest builder is the Swallow. They build a nest made of tiny mud pellets which dry out and form the main frame of the nest. The nest is then lined with feathers and hair before the female lays the eggs. These nests can sometimes be so well built, that they are used year after year, with the returning birds simply doing a little bit of repair work each spring. The smallest bird in Ireland, the Goldcrest, builds the smallest nest. It is made of lichen and moss and lines with feathers and hair. Some tree-nesting birds go one better and build a nest with a roof. The most elaborate nest is that of the Long-tailed Tit. They construct a domed, rugby ball-shaped nest of lichens, spiders webs and feathers. There is an entrance hole at the side. Inside the nest, the incubating adult, the eggs and, when they hatch, the chicks, are warm and snug, away for the elements outside. In many ways, Long-tailed Tits could almost be described as hole-nesters.

Kingfishers are hole nesters and excavate long tunnels in river banks
Hole Nesters
As the name suggests, there are many birds which choose to build a nest under cover. This can be simply a hole in a wall or tree, or, as in many gardens, in specially erected nest boxes. Nesting in a hole offers great advantages. It can be difficult for a predator to attack the nest, eggs or chicks, the nest can't be seen, and finally the adult bird and the eggs/chicks are protected from the weather outside. One of the commonest hole-nester is the Blue Tit. These birds readily take to nest boxes. The male will select the nest site and, once the female gives her approval, both set about creating a nest of grasses and straw. This forms the base of the nest and the female, like the cup-nesters, will create a cup shape that fits snugly around her for the incubation period. The nest will then be lined with feathers and hair... groomed pet hair is a favourite lining. It is ironic to think of young Blue Tits snuggling in against a big ball of cat hair isn't it?

Other nest holing birds are Starlings. These will use holes in walls, trees or even go into holes in roofs of houses. Other birds excavate their own nest holes. Sand Martins (close cousins of the Swallow) will dig out a long entrance tunnel which leads down to a nesting chamber. These are usually found on steep sand dunes and on the faces of quarries. Some have even been known to use the faces of cut-away bogs. Another bird that excavates a nest hole is the Kingfisher. They nest on the banks of rivers and in the Druids Glen, in Wicklow, have even used a specially constructed wall overlooking the river.

The No-Nester
Finally, I can't leave the subject of nests and nest building without mentioning one very special species, the Cuckoo. Cuckoos have evolved a very unique approach to rearing their young. They do not build any nest at all. In fact, they don't have anything to do with raising their families. They lay their eggs in the nests of other species. The eggs are exactly the same colour and pattern of the host species. So as not to raise suspicion, when the female Cuckoo lays an egg, she removes one of the other eggs from the nest. That way, when the host bird returns, she won't think that there are too many eggs in the nest! Once the Cuckoo chick is hatched, it will push all the other eggs and chicks out of the nest and will then receive the undivided attention of the poor host birds that spends their summer feeding this enormous and ever-hungry chick. With no chicks to look after, the adult Cuckoos usually leave Ireland by August and head south at their leisure. The young Cuckoos depart in September, leaving behind very exhausted foster parents.

Whatever the nest design and strategy of nesting, you can be sure that each one is designed to offer the best protection and safety for the eggs and chicks. It is a busy time for parent birds. It is a major investment for themselves and for the future of their species. Here's hoping for a successful breeding season ahead.

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