- The retina of a house sparrow has 400,000 photoreceptors/mm2.
- The cat is the most feared predator of the nestlings, killing them soon after they leave the nest.
- House sparrows are non-migratory birds, but it’s not uncommon for urban flocks to move to the country in late summer to feed on ripening crops.
- Sparrows are some of the few birds of the order Passeriformes that engage in dust, water, or snow bathing.
- Sparrows are social creatures and non-territorial, but they will show aggressiveness to intruders approaching their nest.
- There has been a quick decline – up to 99% - in sparrows’ population in some parts of the world, and they have been included for the first time on the official list of threatened birds.
The house sparrow is a stout, stocky bird, with a different shape compared to other North American sparrows (to which it is not related). The typical length is 16 cm, with a wingspan of 19 cm and an average weight of 28.5 grams. The tail is usually ¾ the length of the wing. The legs are short, the bill is thick and conical, the head is large and rounded, and the chest is chunkier and fuller than indigenous American sparrows.
Regarding color pattern, house sparrows are dimorphic (they exhibit significant visual differences between the genders). Males have a black face and neck, gray crown, and dark brown and black upperparts. They also have white cheeks and black chin and bib, with a rust-colored cap and neck and a pale abdomen with black and brown streaks on the back and wings. Males have only one white wing bar. Females are paler than males, having a buff eye stripe and lighter bill. Juvenile house sparrows are similar in appearance to the female, but have a darker bill and mottling on their crown. House sparrows resemble the Eurasian tree sparrow, common in Victoria and New South Wales, the only difference being the all-brown crown and black cheek patch of the latter.
Diet, Behavior, and Habits
House sparrows have been introduced in North America in the 1850s and are now one of the most common bird species in southern Canada, United States, and Central America. They are very social and highly adaptable to urban and agricultural environments. They are non-migratory but can become nomadic when seeking food resources.
House sparrows are generally monogamous, forming permanent pair bonds for every breeding season. Nesting sites are built in spring from dried vegetation, grass, wool feathers, paper, and finer plant material, and are usually located inside crevices in wall buildings, in coniferous and deciduous tree hollows, under bridges, or in thick vegetation. A clutch comprises 1-8 eggs, and several clutches (up to four, but typically two or three) can be laid in the extended breeding season.
The incubation process starts once all eggs have been laid and includes the participation of both males and females, which incubate the eggs alternatively for 10-14 days. After hatching, both sexes feed the nestlings through regurgitation for another 14-18 days. Both the male and female engage in attacks on intruders found in the proximity of their nesting site (males attack males and females attack only females).
House sparrows find food mostly on the ground, where they move by hopping and scratching with their feet, but also in trees and bushes. In suburban and agricultural habitats, their diet consists primarily of livestock feed (corn, oats, wheat), grains, and insects, while those in urban settings eat commercial birdseed, weed seeds, flower buds, fruit, and food items discarded by humans.
When isolated, house sparrows are quiet, but in large groups, they can be very vocal and disturbing to humans nearby.
Sparrows are non-native invaders that often enter conflicts with humans for the following reasons:
- They are significant crop pests, pecking seeds, buds, flowers, and fruit of grain, oilseed, vegetable, and fruit crops across Canada. Highest losses have been recorded in apple, pear, cherry, apricot, plum, and peach orchards, as well as in tomato, lettuce, peas, wheat, and sunflower crops.
- They consume and spoil livestock food, causing losses at piggeries and poultry farms.
- They cause significant secondary agricultural losses as the exposed flesh of fruit and vegetables encourage the appearance of insects and fungi that continue the damage to crops.
- They can cause floods and property damage as their droppings and nesting materials often clog drains and gutters.
- They fight and kill native bird species in the competition for nesting sites.
- They are a vector of transmission of many diseases to livestock, pets, and humans, including tuberculosis, salmonellosis, Giardia, and infections.
Management and Control
Homeowners can take different measures to reduce house sparrow populations and make life easier for native birds. Control can either be passive or active.
- Habitat modification. Eliminating food sources is often the easiest way to make your property less attractive to intruders. Remove corn, wheat, millet, oats, and bread crumbs from feeders and fill them up with safflower seeds, nectar, fruit, and nuts, if you want to continue feeding native birds. At the same time, remove birdbaths and any other bodies of standing water to prevent sparrows from using them for drinking and bathing, as well as dust patches they use for dust bathing.
- Exclusion. Due to their intelligence and high adaptability, excluding sparrows permanently is often very difficult. Some methods can, however, provide temporary relief, including using PVC boxes (typically avoided by house sparrows, which prefer wood boxes) and denying their access inside birdhouses by making entrance holes smaller than 1 1/2” (although this can also prevent other native birds from entering).
- Trapping. While this method may be more costly and labor-intensive than other control methods, it has been shown to effectively reduce sparrow populations. There are several traps available for sparrows, including funnel or drop-in traps, in-box traps, triggered traps, and elevator traps, all humane and effective methods to trap and remove birds from your backyard. Regardless of what trap is used, the secret to trapping is the pre-baiting period – approximately one week prior to setting up the trap – and selecting the right bait. Both of these operations are best performed by a licensed pest control professional.
- Nest removal. If nesting sites are not removed, house sparrow populations will continue to increase. Removing nests, eggs, and nestlings will dissuade birds from building; however, because they tend to be persistent, the operation must be repeated every two weeks during the breeding season. It is important to make sure that, in their search for a new nesting site, sparrows don’t usurp another active nesting box and kill its inhabitants. Long poles can be used to remove nests, which should be destroyed to prevent reuse.
House sparrows are one of the very few bird species in North America that are not protected by the law, being called by some “flying rats” or “weeds of the air” due to their destructive behavior and because they aggressively compete with native birds for nesting sites. Here are some simple methods to keep house sparrow populations under control:
- Keep the shed doors closed to prevent sparrows from gaining access
- Remove shrubberies, brush piles, and other natural shelter
- Install mesh or nylon netting under the house's eaves
- Put up birdhouses at the end of April, when sparrows' search for a nesting site would have ended
- Relocate birdhouses or consider building them from PVC pipe and making the entrance no larger than 1.25 inches