House Sparrow

Male and female house sparrows will typically grow to be similar sizes, with both sexes capable of reaching a body length of 15-17 cm and wingspans of 19-25 cm (The Cornell Lab of Ornithology). This species displays sexual dimorphism (sexes of the same species display different morphological characteristics); males have more vibrant and distinct colouration (specifically during breeding season), whereas females and juveniles appear more monotone and streaky brown.   

The appearance of males will vary depending on the season. Males will be the easiest to identify throughout the breeding season and display the most distinct markings and colouration, with their patterned heads being the most recognizable during this time. Breeding males have a grey-coloured crown, a rufus/chestnut brown-coloured stripe behind the eye that extends down into the nape, a black throat that sometimes extends into the upper chest, white/light grey lower chest and belly, and brown and black striping located on the wings and mantle (area between the wings on birds’ back). Breeding males will usually have a black beak.  

Following the breeding season, the once vibrant colouration of male house sparrows will begin to fade. They will lose most of their chestnut colouration, grey cap, black throat, and white belly, and overall will appear more dull and streaky brown. The colour of their beaks will also change from a deep black to a light brown/yellow.

Female house sparrows will appear more dusty brown, with a light underbelly and similar brown striping on the wings and mantle. However, unlike males, females will lack any distinct black, grey, and white head markings, and their appearance will remain the same year-round. Females have beaks that vary from light brown to dark grey in colour. 

The breeding season of house sparrows is longer than most native songbirds, running from late March to mid-August. Throughout this breeding season, house sparrows can have 1-3 broods (a set of baby birds hatched at the same time by the same parents) each year. Female house sparrows can lay anywhere from 1-8 eggs per brood with an average of around 3-6 eggs. These eggs are 1.4 – 2.2 cm in length and vary in colouration from pale blue/green to light grey and are covered in small brown speckles (Royal Audubon Society). A single breeding pair is capable of producing 24 eggs a year, or 72 eggs in a lifetime under ideal circumstances. House sparrows will generally breed for life, with both parents involved in raising young (i.e, constructing the nest, incubating eggs, feeding hatchlings, etc.). The incubation period of these eggs can last 10-14 days, with hatchlings ready to leave the nest just two weeks following. It takes 6-9 months for house sparrows to reach sexual maturity after leaving the nest, and their average life span in the wild is around three years (The Cornell Lab of Ornithology).

House sparrows prefer to nest in urbanized areas and are overall closely associated with humans and their infrastructure. They can commonly be found in cities, towns, suburbs, and farms, and are less commonly found in deep forests or grasslands (The Cornell Lab of Ornithology). They prefer to nest in enclosed cavities, and their diet consists mostly of seeds, making a backyard space equip with bird houses and seed feeders the ideal habitat for this invasive species.

House sparrows are a widespread invasive species that thrive throughout most of North America. In urbanized areas, house sparrows will often choose to nest within the holes or crevasses of buildings, rain gutters, drier vents, etc. House sparrows are especially drawn to birdfeeders, birdboxes, and bird baths, meaning the presence of these resources may promote this species from nesting nearby. The most obvious sign and symptom of house sparrow establishment is witnessing an abundance of them within a given area, (i.e., taking over birdfeeders, crowding birdbaths, claiming nest boxes). An abundance of house sparrows can also lead to a decline in native songbird biodiversity. House sparrows are territorial and will act aggressively toward other native songbirds at feeders and bird boxes, ultimately driving them away to find resources elsewhere.

Dead native songbirds and hatchlings found within proximity of their nesting sites could also be a sign of house sparrows establishing. In addition to the aggressive behavior they display at bird feeders, house sparrows are also very intrusive and have been known to take over the nests of native species. Before building a new nest on top of the pre-existing one, house sparrows will kill both adult birds and hatchlings nesting there and destroy any present eggs. In open sites, the nests of house sparrows resemble an untidy globular mass with an exit hole in the side. In enclosed sites such as birdhouses, nesting material is used to line the inside of the box and acts as a foundation. House sparrows have been known to use nesting materials such as grass, weeds, twigs, feathers, and especially pieces of scraps/trash (Royal Audubon Society).

Ecological Impacts

House sparrows are territorial and aggressive towards native songbirds and will compete with them primarily for nesting habitat and resources. House sparrows begin building their nests in March, before the arrival of some native songbirds, giving them the advantage of the first pick at ideal nesting sites and birdboxes over native species. House sparrows will also compete with native songbirds for staple food resources. This behavior can be seen especially at bird feeders where house sparrows will overcrowd and chase other approaching species away. House sparrows disrupt native songbird biodiversity by preventing native species from nesting/reproducing successfully, and by directly killing them. Native species that are particularly vulnerable to the impacts of house sparrows include eastern bluebirds, western bluebirds, purple martins, tree swallows, cliff swallows, and Baltimore orioles (Mayntz, 2021).

Economic & Social Impacts

House sparrows are considered a nuisance to many home and business owners as they are notorious for building nests and tightly packing dry material into inconvenient locations such as holes/crevices in buildings, rain gutters, drier vents, fan vents, street signs, machinery, electric signage and more. Building nests in unsuitable locations such as these can lead to hazards and damage that can be expensive to repair.

Their competitive and aggressive behavior deters native songbirds from visiting backyard nest boxes, bird baths, and bird feeders which can be discouraging not only for these native species but also for avid bird watchers who enjoy viewing native songbirds in their backyard spaces.

There are many different approaches to managing house sparrows, especially in backyard environments. Discouraging house sparrows from nesting in bird houses or from visiting feeders can help keep these resources available for native species.

• Prevent nesting: Because house sparrows begin building their nests earlier in the season than many native species do, it is recommended that the entrances of birdhouses be plugged until early to mid April, or until desired species have arrived. This gives native species a solid chance at claiming these ideal nesting locations. If a house sparrow nesting hole is found, if possible, the nest should be removed, and the entrance holes closed with material, boards, or mesh screening.

• Control food availability: The favorite food items of house sparrows include filler grains like milo, millet, and cracked corn. Controlling the availability of these food items in birdfeeders could discourage this invader from visiting, or at least prevent them from overcrowding.

• Remove house sparrow nests: House sparrows are an invasive species in Ontario and are not protected under the Migratory Birds Act. This means that nests and eggs can legally be removed or destroyed. Before the removal takes place, identification of the nest and eggs is crucial to ensure you are not needlessly damaging a nest belonging to a native species. House sparrows produce large broods multiple times a year. Removing nests and eggs can help decrease population sizes of this invader and help mitigate stress on native species.