House sparrows (Passer domesticus) are one of the most recognisable of the garden birds and have endeared themselves to humans in both urban and rural environments. In 1847, author James Aiken described them as “a most familiar and well-known bird, constantly fluttering round our habitations, streets, fields, barn-yards, gardens, and orchards”. 1
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House sparrow ecology
Bird ringing
Sources
House sparrows belong to a group known as passerines, from the order Passeriformes. Passerines, or perching birds, are grouped this way because of the orientation of their toes, with three pointing forward and a single digit pointing backward. Generally speaking, this diverse group includes the small garden birds that you see flitting around green spaces in hedges and through the trees.
These small, grey-brown birds are sexually dimorphic, meaning that the males and females do not look similar. Males are readily recognized, with a black bib and eye mask, grey cap, and all grey cheek patch. There is also a visible white patch just behind the eye and their bills are typically dark. Females are less obvious, though can be identified by the pale supercilium (the “eyebrow” stripe) and heavily streaked brown, buff, and black wings and mantle or “shoulders”. Females also tend to have pale bills.
Juveniles are difficult to distinguish from females, with an overall buffy brown colour and pale bill. When first fledged from the nest, it may be possible to note bright yellow at the corners of the base of the bill, where the fleshy flanges are, but this can be difficult to see unless the bird is in hand.
House sparrows are highly opportunistic feeders, but their diet is largely vegetarian.
The main foods are grain, seeds, and other vegetation, including buds, berries, and fruits.2 During the busy breeding season, the sparrows will feed on invertebrates, but this makes a small portion of what they eat. Because they are willing to exploit new food sources, house sparrows will readily eat food provided by humans, from bird feeders to food scraps.
House sparrows are very noisy; it is typical to hear these birds before you see them as they chirrup from a nearby hedge or from the eaves of a building. The vocalisations are fairly distinct, short, repetitive notes. These calls act as a communication between members of the flock—contact calls—but during the breeding season, the males call more frequently to attract females and broadcast their reproductive availability. 3
In the UK, breeding season typically starts in March and runs through to late summer. The house sparrows are cavity nesters, meaning that they construct their nests in natural holes in trees or previously-built nests from other species, including swallows, though they can also be found nesting in hedges. Through their close association with human settlements, they are commonly found nesting in the eaves of houses, in the nooks and crannies of older buildings, and other gaps and crevices that they can squeeze into with nesting material. In line with this ability to exploit new opportunities, sparrows take readily to nest boxes. As they are a highly gregarious species, the house sparrows prefer to nest in close proximity to their colony mates and will actively look for suitable sites.
Males begin construction of the nests, though females will assist once a suitable mate has been chosen.2 Materials used include twigs and grasses for the main structure, which is then lined with mosses and feathers. The female will lay between three to five eggs, incubating them for approximately 12 days. 4 Male birds will help with incubation duties, but the majority is done by the female.
Like all passerines, house sparrow nestlings are altricial: they are naked and blind at birth and completely dependent on their parents for food and warmth. After a week, the nestlings will have their first set of feathers grown in and by the second week, the young birds will be getting restless, stretching their fully-feather wings and moving around their confines. During this time, both parents feed the chicks. While the adults are mainly vegetarian, the young are given a high-protein diet of invertebrates to help them grow quickly before they leave the nest. 2
The young will fledge at about 14 days, but they are not yet independent: their parents continue to feed them for another week before they must feed themselves. 4 The young sparrows require less and less parental care, leaving the parents free to set up another nest. House sparrows will make two to three nesting attempts over a single breeding season under optimal conditions.
Bird Ringing
There are many ways that researchers can study species, but one of the most effective and wide-spread is ringing. Ringing schemes are overseen by various governing bodies that are responsible for training, supply, and documentation. In the UK, the British Trust for Ornithology (BTO) manages the ringing scheme. Under BTO guidance, ringers work through an intensive training process to earn a ringing license.
The rings themselves are small metal loops with unique identifying codes printed into them. They are made in different sizes and styles, which accommodate the great variety of bird legs that they are put on: rings for a small house sparrow would not work on a herring gull and a herring gull’s ring would not keep on a house sparrow! Even within the garden birds, there is a great variety of size; at times, ring sizes will even differ between male and female birds.
Biologists also use colour rings—small coloured-plastic rings, comparable to the metal ones—to further study birds in the field. The colour rings allow researchers to study the birds without need for repeated capture, so it can help to minimise stress while the birds are still being studied.
We can learn a lot about birds through the use of rings: they allow us to determine longevity and help us understand species’ movements. By collecting morphometric data while the birds are in hand, we gain detailed information about body structure and size, which can be used to differentiate species and even sexes, as well as environmental influence on populations. Measurements like these support the ecological rule that birds within a species are typically larger as the populations approach the poles (known as Bergmann’s rule). Colour ringing in particular can help improve our understanding of mate selection, dispersal, and colony structure.
How we get the rings on the birds
Ringers use special equipment to capture and mark birds. The first tool at their disposal is the mist net. These nets are made of fine mesh that are difficult for the birds to see. Nets can range from 3 to 18 metres in length and 1 to 4 metres in height. Even the holes of the nets can differ in size depending on the species you are targeting, though 16mmx16mm is fairly standard.
The nets have several “trammels” that run the length at regular intervals; these allow the nets to drape at each interval, creating “bags”. It is this feature that captures the birds: when a bird flies into the net, they fall into the bag and become trapped. Nets are checked regularly to ensure that birds are not left for too long.
Note: If you find a bird in a net, it is best to not disturb it. Standing too closely—or attempting to remove the bird yourself—can cause distress and injury to the bird. Ringers are trained in proper techniques to safely remove birds and minimize stress. If you are worried for the bird’s safety, tell the ringer that there is a bird in the net or wait quietly nearby, keeping distance to minimize stress. Keep pets away from the area at all times.
Other tools used when ringing birds include bird bags, ringing pliers, a wing ruler, a small scale, and tubes with which to weigh the birds.
Want more info?
Learning to ring takes practice and dedication. The first step to becoming a ringer is locating a trainer that can help you learn to work with the mist nets and handling birds. If you are interested in the UK ringing scheme, contact the BTO for more information.
Sources
1 Aiken, James (1847). A Natural History of Beasts, Birds, & Fishes, Or, Stories of Animated Nature. Edinburgh: Thomas Nelson.
2 Anderson, Ted R. (2006). Biology of the Ubiquitous House Sparrow: From Genes to Populations. Oxford: Oxford University Press.
3 Summers-Smith, J. Denis (1963). The House Sparrow. New Naturalist (1st ed.). London: Collins.
4 Summers-Smith, J. Denis (1988). The Sparrows: a study of the genus Passer. London: A&C Black Publishers; (online edition: 2010. London: T&AD Poyser)