The fish crow (Corvus ossifragus) is a medium-sized crow that is found in coastal regions of eastern North America. Both male and female fish crows exist, and can be differentiated based on size, coloration, and calls.
Appearance
Male and female fish crows have similar plumage, but males tend to be slightly larger. On average, male fish crows measure around 17-21 inches (43-53 cm) long, while females measure 16-19 inches (41-48 cm). Wingspans range from 33-39 inches (84-99 cm) across for males and 31-37 inches (79-94 cm) for females. In terms of weight, males tip the scales at around 11.2-16 ounces (316-453 grams) on average and females weigh approximately 9.5-14 ounces (269-396 grams).
Both sexes have black feathers covering most of their body. The black plumage has a blue or purple iridescent sheen when seen in direct sunlight. The throat and upper breast of the fish crow are a dull gray-white color. The eyes, bill, and legs are also black.
Female fish crows tend to have slightly duller plumage overall compared to males. Females also have thinner, less robust bills than males. However, these differences in coloration and bill size are quite subtle and variable, making sexing by appearance alone challenging.
Size Comparison
Feature | Male | Female |
---|---|---|
Length | 17-21 in (43-53 cm) | 16-19 in (41-48 cm) |
Wingspan | 33-39 in (84-99 cm) | 31-37 in (79-94 cm) |
Weight | 11.2-16 oz (316-453 g) | 9.5-14 oz (269-396 g) |
Voice
The calls of male and female fish crows also differ somewhat. Males tend to have lower-pitched, raspier sounding voices than females. The familiar “caw caw” sound of the fish crow is noticeably huskier in males. Females vocalize at a higher pitch, producing a sharper “caw”.
To human ears, a male fish crow’s typical call could be described as a gravelly “caah caah”. Meanwhile, a female’s call is more of a staccato “caw caw” with less raspiness. The male’s voice carries well and can be heard at greater distances than the female’s. This likely helps males effectively advertise and defend territories.
Behavioral Differences
Certain behavioral differences also exist between male and female fish crows that can aid identification.
Male fish crows are highly territorial during the breeding season. They defend nesting and feeding areas aggressively, chasing away other males through vocalizations and physical attacks. Females do not exhibit the same level of territorial behavior.
Additionally, male fish crows devote more time to bringing food to incubating females at the nest. Females primarily remain at the nest and rarely leave once egg laying starts. The male parent takes responsibility for most of the hunting and foraging to provision his mate and subsequent young.
Males also perform courtship displays for females at the onset of breeding season. Elaborate aerial maneuvers, bowing motions, and offerings of food gifts help form pair bonds. Females may solicit courtship from desirable males but primarily play a receptive role.
Other Clues for Sexing
If observed directly, a few other characteristics can help determine the sex of a fish crow:
- Females develop a brood patch during breeding season – this is a bare area on the belly that aids egg incubation.
- Females alone build the nest, typically high up in a conifer tree.
- Females alone incubate eggs and brood hatchlings.
- Females have a wider pelvic girdle to aid in egg laying.
Breeding Behavior
Male and female fish crows take on distinct roles and duties during the breeding season, which further highlights their sexual dimorphism.
Breeding occurs early in the year, normally between March and May depending on latitude. Nests are constructed by females in the tops of mature trees, either in natural forked branches or on artificial platforms like telephone poles.
Females lay between 4-6 light blue or green eggs with brown splotches. They incubate the eggs for about 18 days before hatching. The male guards and patrols the territory, driving off threats like hawks, owls, or other crows.
Once the helpless young hatch, the female broods and feeds them initially. The male now ramps up hunting, bringing plenty of food to feed the female and growing hatchlings. Both parents feed and care for the young as they grow and fledge at around 1 month old.
By paying attention to nest building, incubating, and brooding behavior, the sex of a given adult fish crow can be confidently determined during breeding season.
Juvenile Fish Crows
Juvenile fish crows are difficult to sex based on size, voice, and appearance. Both males and females closely resemble adults at this stage but in more muted, soft plumage overall.
Juvenile crows only start to show distinctive male and female traits after reaching sexual maturity at around 2 years old. Prior to maturity, male and female young look and sound essentially identical in the field.
Conclusion
While male and female fish crows are hard to differentiate by casual observation, careful attention to size, voice, and role during breeding can reliably indicate the sexes. In particular, nest building, egg incubating, and brooding signify an adult female fish crow. Conversely, food provisioning and aggressive territorial defense are trademarks of a virile male. So next time you encounter a fish crow, listen and watch closely for these tell-tale clues to determine if you’re looking at a male or female!