page_title: Tree swallow
section_title: Breeding
hierarchical_section_title: Tree swallow / Behaviour / Breeding
caption_attribution_description: Deutsch: Sumpfschwalbe Tachycineta bicolor , Ei, Coll. Museum Wiesbaden English: Tree swallow Tachycineta bicolor , egg, Coll. Museum Wiesbaden
context_page_description: The tree swallow is a migratory bird of the family Hirundinidae. Found in the Americas, the tree swallow was first described in 1807 by French ornithologist Louis Vieillot as Hirundo bicolor. It has since been moved to its current genus, Tachycineta, within which its phylogenetic placement is debated. The tree swallow has glossy blue-green upperparts, with the exception of the blackish wings and tail, and white underparts. The bill is black, the eyes dark brown, and the legs and feet pale brown. The female is generally duller than the male, and the first-year female has mostly brown upperparts, with some blue feathers. Juveniles have brown upperparts, and a grey-brown-washed breast. The tree swallow breeds in the US and Canada. It winters along southern US coasts south, along the Gulf Coast, to Panama and the northwestern coast of South America, and in the West Indies.
  The tree swallow nests either in isolated pairs or loose groups, in both natural and artificial cavities. Breeding can start as soon as early May, although this date is occurring earlier because of climate change, and it can end as late as July.
context_section_description: The tree swallow nests in structures with pre-existing holes, both natural and artificial. These were once found only in forested regions, but the building of nest boxes has allowed this bird to expand into open habitats. This swallow usually nests in the area it bred the year before; only about 14% of females and 4% of males disperse to breed at a new site per year. Most do not go far, usually breeding at sites less than 10 kilometres (6.2 mi) away from their original grounds. Dispersal is influenced by breeding success; of the adult females that fail to fledge a chick, about 28% disperse, compared to 5% of successful breeders. Natal dispersal (when a bird does not return to the site it was born at to breed) is common in the tree swallow and occurs more frequently than breeding dispersal. It nests both in loose groups and isolated pairs. When nesting in loose groups, nests are usually spaced at least 10 to 15 metres (33 to 49 ft) apart, and those that are closer in distance are usually further apart in terms of laying date. In natural cavities, the tree swallow nests about 27 metres (89 ft) apart from its neighbor. The nest hole in these situations is, on average, 3.4 metres (11 ft) above ground level, although about 45% of them are less than 2 metres (6.6 ft) above the ground. Higher cavities are likely favoured because they reduce predation, while lower nest holes may be chosen to avoid competition. Entrance widths are often between 4 and 5 centimetres (1.6 and 2.0 in), whereas entrance heights are more variable: a 1989 study found openings ranging from 3.5 to 26 centimetres (1.4 to 10.2 in). Cavity volume is generally below 1,000 cubic centimetres (61 cu in). After finding a suitable place to nest, the male perches near it and calls frequently. A lack of sites can cause fights between birds, sometimes resulting in deaths. This swallow usually defends an area around the nest with a radius of about 4.6 metres (15 ft), as well as extra nests inside of that territory, by blocking the entrance to the nest and chasing intruders. The nest cup itself is made from grass, moss, pine needles, and aquatic plants collected mostly by the female, and is lined with feathers gathered primarily by the male in fights. The feathers may function to insulate the nest, decreasing incubation time and likely preventing hypothermia in chicks. In addition to faster growth for chicks, eggs cool slower in nests with feathers than those without. However, a study published in 2018 did not find a significant correlation between the number of feathers in nests that were artificially warmed versus those that were not. Additionally, it found that nests in St. Denis, Saskatchewan used significantly less feathers than those in Annapolis Valley, despite the former being further north. However, temperatures in Nova Scotia (where Annapolis Valley is) are generally lower than those in Saskatchewan, possibly explaining the unexpected result.
  During courtship, a male tree swallow attacks an unknown female. This can be stimulated through wing-fluttering flight by the female, which may be an invitation to court. The male may then take a vertical posture, with a raised and slightly spread tail and wings flicked and slightly drooped. This prompts the female to try to land on the male's back, but he flies to prevent this; this is repeated. After courting the female, the male flies to his chosen nest site, which the female inspects. During copulation, the male hovers over the female, and then mounts her, giving ticking calls. He then makes cloacal contact with the female while holding her neck feathers in his bill and standing on her slightly outstretched wings. Copulation occurs multiple times.
  Eggs are laid from early May to mid-June (although this is happening earlier due to climate change) and chicks fledge between mid-June and July. Latitude is positively correlated with laying date, while female age and wing length (longer wings allow more efficient foraging) are negatively correlated. The tree swallow is likely an income breeder, as it breeds based on food a
caption: A tree swallow egg
exif: {"Image Make": "NIKON CORPORATION", "Image Model": "NIKON D90", "Image Orientation": "Horizontal (normal)", "Image XResolution": "300", "Image YResolution": "300", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "GIMP 2.8.10", "Image DateTime": "2014:12:03 13:13:11", "Image YCbCrPositioning": "Co-sited", "Image ExifOffset": "222", "GPS GPSVersionID": "[2, 2, 0, 0]", "Image GPSInfo": "10078", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "300", "Thumbnail YResolution": "300", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail YCbCrPositioning": "Co-sited", "EXIF ExposureTime": "1", "EXIF FNumber": "16", "EXIF ExposureProgram": "Aperture Priority", "EXIF ISOSpeedRatings": "200", "EXIF ExifVersion": "0221", "EXIF DateTimeOriginal": "2012:07:13 15:22:46", "EXIF DateTimeDigitized": "2012:07:13 15:22:46", "EXIF ComponentsConfiguration": "YCbCr", "EXIF CompressedBitsPerPixel": "4", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "5", "EXIF MeteringMode": "Pattern", "EXIF LightSource": "Unknown", "EXIF Flash": "Flash did not fire", "EXIF FocalLength": "85", "EXIF SubSecTime": "00", "EXIF SubSecTimeOriginal": "00", "EXIF SubSecTimeDigitized": "00", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "0", "EXIF ExifImageLength": "0", "Interoperability InteroperabilityIndex": "R98", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "EXIF InteroperabilityOffset": "10048", "EXIF SensingMethod": "One-chip color area", "EXIF FileSource": "Digital Camera", "EXIF SceneType": "Directly Photographed", "EXIF CVAPattern": "[0, 2, 0, 2, 1, 2, 0, 1]", "EXIF CustomRendered": "Normal", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Manual", "EXIF DigitalZoomRatio": "1", "EXIF FocalLengthIn35mmFilm": "127", "EXIF SceneCaptureType": "Standard", "EXIF GainControl": "None", "EXIF Contrast": "Normal", "EXIF Saturation": "Normal", "EXIF Sharpness": "Normal", "EXIF SubjectDistanceRange": "0"}