The American kestrel (Falco sparverius), also called the sparrow hawk, is the smallest and most common falcon in North America. It has a roughly two-to-one range in size over subspecies and sex, varying in size from about the weight of a blue jay to a mourning dove. It also ranges to South America and is a well-established species that has evolved into 17 subspecies adapted to different environments and habitats throughout the Americas. It exhibits sexual dimorphism in size (females being moderately larger) and plumage, although both sexes have a rufous back with noticeable barring. Its plumage is colorful and attractive, and juveniles are similar in plumage to adults. Under traditional classification, the American kestrel is the smallest raptor in America. The American kestrel is sexually dimorphic, although there is some overlap in plumage coloration between the sexes. The bird ranges from 22 to 31 cm (8.7 to 12.2 in) in length with a wingspan of 51–61 cm (20–24 in). The female kestrel is larger than the male, though less so than larger falcons, being typically about 10_ to 15_ larger within a subspecies. The more northern subspecies tend to larger sizes, with a large northern female being about twice the size of a small southern male. The male typically weighs 80–143 g (2.8–5.0 oz), and the female 86–165 g (3.0–5.8 oz). In standard measurements, the wing bone is 16–21 cm (6.3–8.3 in) long, the tail is 11–15 cm (4.3–5.9 in) and the tarsus is 3.2–4 cm (1.3–1.6 in).
The American Kestrel occurs throughout the Western Hemisphere including the West Indies, where it is generally a common resident in The Bahamas, Greater Antilles, Virgin Islands, and the Lesser Antilles (Raffaele and others 1998). It is a common nesting species in Puerto Rico (Oberle 2018) and a common resident on Vieques (Gemmill 2015). It also occurs in Mona and Culebra (Biaggi 1997, Ventosa-Febles and others 2005). This species occurs throughout Puerto Rico but is observed most commonly in the dry regions of the southern side of the island (Biaggi 1997) and inhabits farms, pastures, open country (Oberle 2018), forest edges, and urban areas like towns and even cities (Raffaele and others 1998). The atlas fieldwork yielded a total of 537 records within 327 hexagons or 68 percent of the 479 total hexagons (see map). Of the 327 hexagons where this species was found, breeding met the atlas definition of confirmed in 17 percent (56) of the hexagons, probable in 26 percent (84), and possible in 57 percent (186), while the species was observed in an additional hexagon (<1 percent) but without evidence of breeding (see map). American Kestrel distribution. The map shows the highest breeding code by hexagon and overlaying the ecological life zones in Puerto Rico. Note: percentages may not total 100 due to rounding. 183American Kestrel/Falcón Común
The American Kestrel is a secondary cavity nestera species that does not make its own cavities but uses the cavities excavated by other species (i.e., woodpecker cavities in trees) or natural cavities in cliff faces (Raffaele and others 1998). Therefore, the species and its distribution may be limited by absence of suitable cavities for nesting. Atlas results indicate that the breeding season for this species extends throughout the year, but breeding is most active from March to June, with a peak in June (see chart). This seasonal pattern of breeding appears to coincide in each of the ecological life zones with no evidence to suggest that breeding times differ among the life zones. Atlas results show that the American Kestrel mostly breeds within the subtropical moist forest life zone (58 percent of the hexagons), followed by the subtropical dry forest life zone (23 percent of the hexagons) and the subtropical wet and lower montane wet forest life zones (19 percent of the hexagons), and rarely breeding in the subtropical rain forest life zone (see table and map).
The American Kestrel is listed as a species of least concern by the IUCN (BirdLife International 2016). Locally, this species is not listed in any of the threatened categories of PRDNER and USFWS. In Puerto Rico, the American Kestrel has a protected habitat in land of 11.5 percent or 902 km2 of the total area covered by the hexagons where evidence of breeding was found for this species (7799 km2).