Saturday, February 22, 2020

Where do Dark-eyed Juncos like to nest?

Dark-eyed Juncos summer in forest openings in northern parts of North America and in forested mountains in the West. Up to 66% of all Dark-eyed Juncos nest in the boreal forests. In winter they move south and are found in most of the United States. They are a common feeder bird in winter.

If you have Dark-eyed Juncos in your area year round can you entice them to nest in your backyard?

Dark-eyed Juncos build an open cup nest on the ground, often in tall grass against or under a root ball or tree trunk. The nest is often hidden by overhanging vegetation such as ferns or other dense plants. They do not use nest boxes. They may, however, nest in undisturbed potted plants on the ground or even hanging pots!

This article is a supplement to my overview page on Dark-eyed Juncos. The overview page leads to other articles on Dark-eyed Juncos, including where they live, what they look like, and what they eat. This page discusses courtship, nesting and reproduction.

Photo of Dark-eyed Junco nest. Cup nest with 4 white eggs spotted with brown and hidden among grass
Dark-eyed Junco nest and eggs
Image by karchicken from Pixabay

Nesting habits and reproduction of Dark-eyed Juncos


Male juncos arrive on territory before the females. Males start singing in March and April. Males sing from a high, conspicuous perch. The males chase off other males invading their territory.

Males court the female. Then the female chooses the nest site and she builds the nest, usually concealed on the ground.

After the female lays the egg, she incubates the eggs until they hatch. Both parents feed the nestlings and continue to do so for a couple of weeks after the young leave the nest.

Juncos are monogamous during the nesting season, but may choose new mates each year. Actually, these birds are "socially monogamous." The pair stays with their one mate raise the young together. However, both birds may frequently copulate with juncos in adjoining territories.

Females that lose their mate through death quickly mate with a neighboring male who may have their own nest and young to care for. These "single moms" take care of raising their own young by themselves.

Dark-eyed Juncos usually breed for the first time when one year old. They usually produce two broods per year, sometimes three. Nest predation is very high. Eggs and young are preyed upon by rodents in the forest.

Courtship and mating


Male juncos arrive on the breeding grounds well before the females. They begin singing from tall exposed perches. They defend their territories vigorously against other male juncos. Territories may be 2-3 acres in size.

The song is a simple musical trill on one pitch.

Dark-eyed Junco pairs are formed in April. Courting males fan their wings and tails and hop up and down. They pick up moss or nesting material to present to the female. Males chirp and sing their trilled songs as they court the female.

Males of the mated pair stay quite close to the females at all times except if chasing away other male juncos from the territory.

Here is a video showing habitat and singing of a male Dark-eyed Junco on territory. (I hear lots of different birds besides the junco singing, though.)


Nest building


The female Dark-eyed Junco does most of the nest building herself. The male may help by bringing nest materials for her to add. The birds may take up to 9 days to complete the nest.

Nests are usually placed on the ground. Nests are well hidden under roots or against tree trunks. They may be covered by bushes or tufts of grass (see photo at top of page). They often have some kind of overhanging shelter over the nest.

Nests are cup-shaped and made of grasses and plant fibers. Nest material may include twigs, moss, and bark strips. The inside of the nest is lined with grass and mammal hair.

I have found conflicting information on whether juncos reuse their nests. It appears that even with successive broods in the same year, Dark-eyed Juncos usually build new nests each time. This makes sense, as a nest, especially on the ground, is likely to be infested with mites and lice and other insects after raising 3-6 nestlings. Nevertheless, juncos do, sometimes, reuse their nest.

Nest boxes


Dark-eyed Juncos will not use nest boxes. However, they may nest in large flower pots with bushy flowers or plants, including rarely hanging flower pots.

A first nesting of a junco in a nest box in Washington Sate in 2016 earned an article in the Wilson Journal of Ornithology (pdf abstract). That's how rare it is for this species (or most related New World sparrows) to nest in a box.

While juncos won't use nest boxes, you may still attract Dark-eyed Juncos to nest in your backyard. The key is allowing a bit of unkempt or natural yard.

Plant several dense spruce trees with branches near the ground. Keep the area around the trees unmanicured so that tall grass grows up. This may work to entice juncos to nest. Other dense bushes with leaves to the ground along a wooden fence may also work. Even a dense flower garden may provide nesting grounds (see video below).

Obviously, ground nesting birds need protection from cats and other predators. So if you suspect nesting in your backyard, please don't look for the nest. If you look for the nest, you will trample a path up to the nest that predators may follow. You may also step on the hidden nest yourself.

Eggs


Dark-eyed Juncos lay eggs as early as March. But since they may nest up to 3 times a season, they may have eggs in the nest as late as August. They lay from 3-6 eggs, frequently 4-5. Early clutches are more likely to have more eggs, later clutches fewer.

In Oregon, nests with eggs or young were found from April 25th to early August. Lowland nesting was earlier than in the mountains (Birds of Oregon: a general reference).

In the mountains of San Diego County, Dark eyed Juncos were noted building nests as early as April 18 and feeding young as early as May 13. However, right along the coast in San Diego, birds build nests as early as February and fledge their last set of chicks in August and September (San Diego County Bird Atlas).

Eggs have a white or gray base color, often with a bluish or greenish hue. They are lightly speckled with brown, mostly on the larger end of the egg. Eggs are about 0.8 inches long.

Females alone incubate the eggs. Eggs are incubated 11-13 days before they hatch.

Here is a video of a junco nest with very young nestlings. How many babies (chicks) do you count?The mother junco has lost her tail. Toward the end of the video the father junco comes in to feed the young. He has a blacker head... and a full tail!


Young--nestlings and fledglings


Young hatch naked and helpless (altricial). The nestlings remain in the nest for 10-13 days.

Both parents feed the nestlings. Young are fed mostly insects.

Young birds leave the nest in juvenile plumage. They appear as small brown sparrows with brown streaks on the breast. The flashing white tail feathers and twittering calls quickly give away their identity. Parents accompany and feed the fledglings for about 3 weeks before they are on their own.

The juvenile plumage lasts 2 to 3 months before they molt into an adult-like plumage. Newer bird watchers aren't fooled very long by the sparrow-like plumage of juvenile Dark-eyed Juncos. They behave as adult juncos, with perhaps even more flashing of their white outer tail feathers.

Here is a video of a juvenile Dark-eyed Junco taking a bath and drying off. The pink bill and white outer tail feathers give away the identification immediately.




Back to the Overview page for Dark-eyed Junco.

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