Nuthatches are small, agile songbirds known for their distinctive ability to move headfirst down tree trunks, accomplished by their strong feet and long claws. This unique climbing style allows them to forage for insects in bark crevices that other birds might miss. Their nesting habits are equally specialized, focusing on securing existing shelters rather than building a traditional open cup nest like many common backyard species. This focus on cavities defines their breeding strategy.
Primary Nest Locations
Nuthatches belong to a group of birds known as secondary cavity nesters, meaning they overwhelmingly rely on pre-existing holes for their nests. These birds seek out natural tree cavities, which form through decay, or abandoned nest holes created by woodpeckers in dead or dying trees. The presence of snags, or standing dead wood, is therefore a fundamental requirement for suitable nuthatch habitat.
Cavities in snags offer a protected, insulated space, and the loss of mature forests and dead trees directly reduces nesting opportunities for these birds. While some species, like the White-breasted Nuthatch, may use nest boxes, they are generally less inclined toward manufactured homes than other cavity nesters. The site is typically chosen in a tree trunk or large limb, sometimes only a few feet off the ground, but often much higher.
The male may play a role in selecting the site, but the female usually makes the final decision. Nuthatches sometimes use an existing hole that is larger than necessary, though some species can modify the entrance. The Pygmy Nuthatch, for instance, frequently adapts and enlarges an existing cavity to suit its needs.
Nest Excavation and Material Use
Once a suitable cavity is selected, the birds begin preparing the interior space for egg-laying. The female typically undertakes the task of building the nest cup within the cavity, using a variety of soft, insulating materials to create bedding for the eggs and young.
Common lining materials include shredded bark, fine grasses, moss, lichens, and animal fur or hair. Some species, like the White-breasted Nuthatch, may incorporate lumps of dirt or dried mud into the base of the nest before lining the cup. The lining is dense and soft, designed to maximize insulation within the confines of the tree hole.
Some species exhibit a unique behavior by applying material around the entrance hole. The Red-breasted Nuthatch, for example, smears conifer resin, or pitch, around the rim of its nest entrance. This sticky substance is thought to serve as a deterrent to predators or larger competing birds that might attempt to enter the cavity. The Eurasian Nuthatch exhibits a similar behavior, plastering the entrance with mud to reduce the opening size, which helps exclude larger cavity competitors.
Seasonal Timing and Parental Roles
Nesting begins in early spring, with nuthatches inspecting and preparing sites as early as March, though egg-laying occurs from April through May. They usually produce a single brood per year, with clutch sizes ranging from five to nine eggs, depending on the species. The eggs are creamy white with speckles of reddish-brown.
The female is the sole incubator, sitting on the eggs for an incubation period that lasts 12 to 14 days. During this time, the male assumes the responsibility of feeding the female, bringing her food to the nest cavity to maintain her strength. Both parents share the role of feeding the nestlings once they hatch.
The young remain in the nest for 18 to 26 days before they are ready to fledge. Even after leaving the nest, the fledglings continue to be fed by the parents for up to two more weeks as they learn to forage for themselves in the forest environment.