Cattle Egret

African Savanna

Location

In the Zoo

Scientific Information

Scientific Name: Bubulcus ibis
Class: Aves
Order: Pelecaniformes
Family: Ardeidae
Genus: Bubulcus

Size

Male

Female

Height: 18-22 inches 18-22 inches
Wingspan: 35-38 inches 35-38 inches
Weight: 9.5-18 ounces 9.5-18 ounces
Maturity: 2-3 years 2-3 years

Lifestyle and Lifespan

Diet: Carnivorous
Activity Timeframe: Diurnal
Interactivity: Social
Sexual Dimorphism: No
Gestation: 24 days
Lifespan in the Wild: 17- 23 years
Lifespan in Captivity:

Geographic Range

The Cattle Egret was once native to subtropical and tropical Asia and Africa, and the southern part of Spain. However, since the 1870's, this species has slowly been colonizing all other continents except Antarctica and is considered a cosmopolitan species. It is present in Africa, Asia, Europe, North and South America, and Australia. Its range on these continents is limited to tropical, subtropical, and temperate climates. The northern limit of its range seems to be just into Canada in North America, and southeastern China in Asia.

Conservation

Status in the Wild: Least Concerned
Threats:

Characteristics

The Cattle Egret is a stocky bird with a hunched figure, and white plumage all over, and dull yellow legs and beak. The neck is thicker than other egrets, and the legs shorter. During breeding season, the Cattle Egret will develop buff or pale gold plumes on the head, chest, and wings. The beak, legs and irises will turn a bright red during this time. Juveniles have dark legs and bills.

Species Specifics

The Cattle Egret is sometime confused with the Snowy Egret where their ranges overlap. The Cattle egret is a lot stockier, with a thicker, shorter neck, and develops pale gold plumes during breeding season while the Snowy Egret keeps its white plumage year-round. The Cattle Egret has two subspecies, the Western Cattle Egret and nominate species (B. ibis) and the Eastern Cattle Egret (B. ibis cormorandus). The eastern subspecies is breeds in Asia and Australia, while the western subspecies is found throughout the rest of the range. Until recently, some scientists categorized them as completely separate species.

Physical Characteristics

The blue color of the Cattle Egret's eggs (as well as other birds, such as the American Robin) is thought to shield the egg from UV radiation while also preventing overheating of the egg, both of which is harmful to the chick inside.

Ecology

Habitat

Unlike other herons and egrets, they are more typically associated with dry open grassy areas, such as meadows, livestock pastures, semi-arid steppes, and savannahs subject to seasonal inundation, and less often flood plains, wet pastures and shallow marshes.

Distribution

Not enough information is known about the home range or population density of the Cattle Egret. They are a partially migratory species, with some populations remaining sedentary depending on food availability and weather. Young Cattle Egret may disperse long distances, as many as 5,000 kilometers (3,100 miles). They also have a tendency to wander extensively.

Diet

Cattle Egrets eat primarily insects and invertebrates, but will also small amphibians, mammals, and other birds.

Ecological Web

The Cattle Egret has a commensal symbiotic relationship with cattle and other large herd animals: by perching on the backs of grazing herd animals and catching the disturbed insects as the herd animals move, the Cattle Egret can get up to 50% more food than foraging by itself while using a third less energy. The herd animals (livestock, rhinoceros, hippos, wild buffalo, elephants, giraffes, elands, waterbuck, etc.) are unaffected by the birds, as the birds weigh too little to be a burden.

Activity and Behavior

Activity Pattern

In the morning, Cattle Egret leave their communal roost to feed. They will be feeding morning and afternoon, with a midday rest. About an hour before sunset, they return to their roosting colonies for the night.

Behavior

During breeding season when the Cattle Egret is in breeding plumage, the erection of crest plumes is indicative of the birds' level of antagonism.

Social Behavior

Cattle Egrets are a very gregarious bird, roosting and breeding and feeding in large mixed species flocks, as well as associating with other species, such as livestock. They perch on the backs of large grazing animals to eat the organisms that are disturbed by the larger animal's movement.

Reproductive Behavior

The start of breeding season is marked by males establishing a territory within a mixed species breeding colony and then attracting a female from there. Courtship displays by the male include stretching out the neck and raising the pale gold plumes on their head while swaying side to side. Males also take short flights with exaggerated wing beats. Females arrive in groups and eventually pair bond with males. Pair bonding lasts only for the season, though at times there may be more than one female pair bonded with a single male. Prior to the bonding, the female will attempt to subdue the male by landing on top of him. Once bonded, both males and females defend the territory.Nests are built each season, though some are reused. Cattle Egrets will roost with other herons and wading birds. Nests are built out of sticks and vegetation in any place that will support a nest. Males retrieve or steal material and the female uses the material to build the nest. Nest maintenance and building continues through incubation and hatching. When one of the pair leaves the nest, upon returning the bird on the nest will perform the Greeting Ceremony by raising the plumes on the back while flattening the plumes on the head. The female will lay between 3 and 4 sky blue eggs, but will not begin seriously incubating until all eggs have been laid. Males and females share incubation duties, which lasts about 24 days. Once the eggs hatch, the first 10 days the male and female will take turns shading the chicks from the sun with their wings and brooding. They may accept other unrelated chicks, so long as they are younger than about 14 days.

Offspring

3-4 eggs, laid about every 2 days. Eggs are a sky blue and lighten as they get older. Chicks hatch after about 24 days, completely dependent upon the parents. Young chicks need constant brooding and shade from the sun. Around 4-8 days, the chicks begin aggressively begging for food, and sibling aggression is common. Between 14 and 21 days, chicks may venture out of the nest by climbing. These are called 'branchers.' They fledge between 25 and 30 days, and are independent at around 45 days.

Conservation

Status

The Cattle Egret is listed as Least Concern (2015) on the IUCN, and has no special status on CITES. It is protected by the US Migratory Bird Act.

Historical

The Cattle Egret was originally native to tropical and subtropical Africa and Asia as well as southern Spain, but has become a cosmopolitan species in the last 60 or so years. In 1877, the species reached South America and continued to spread over the continent. However, it wasn't 1941 that they were spotted in North America and confirmed to be breeding in North America in 1953, reaching Canada in 1962. Australia was colonized in the 1940's, and the European range expanded in the 1960's, reaching Italy in 1985. It was recorded as breeding in the United Kingdoms and spotted in Fiji in 2008.

Current Threats

Our Role

The Oakland Zoo is partnered with Golden Gate Audubon Society, which focuses on birds living in urban areas, such as the Bay Area. Recently, Golden Gate Audubon Society and the Oakland Zoo worked together to help rescue relatives of the Cattle Egret, the Black-crowned Night Heron and the Snowy Egret, when fledglings of these species were found fallen from their nest in Downtown Oakland. http://www.oaklandzoo.org/Press_Releases.php?c=GGAS_Heron_Rescue

How You Can Help

Since Cattle Egrets nest in trees, and sometimes in urban areas, be mindful of when you trim your trees, and either take a class on bird-friendly tree trimming, or hire an arborist that is ISA certified.

Fascinating Facts

Many of the different colloquial names for the Cattle Egret have an association with farms, livestock, or large grazing animals. Even their genus name, Bubulcus, means herdsman in Latin

The Cattle Egret now outnumbers all other populations of herons and egrets in North America put together.

In some agricultural areas, the Cattle Egrets follow the tractors through the fields and eat the animals the tractor disturbs.

Some farmers rely on the Cattle Egret for fly control more than they do pesticides!

It has been found that Cattle Egrets selectively forage around animals that take only 5-15 steps per minute, avoiding slower and faster herd animals.

Cattle Egrets engage in low-level brood parasitism, sometimes laying their eggs in the nests of other Cattle Egrets or even Snowy Egrets or Little Blue Herons.

References

http://www.iucnredlist.org/details/22697109/0

http://eol.org/pages/1048666/details

https://www.beautyofbirds.com/cattleegrets.html

https://www.allaboutbirds.org/guide/Cattle_Egret/id

http://www.audubon.org/field-guide/bird/cattle-egret

http://www.arkive.org/cattle-egret/bubulcus-ibis/

http://animaldiversity.org/accounts/Bubulcus_ibis/

http://www.sms.si.edu/irlspec/Bubulcus_ibis.htm

P.O. Box 5238

9777 Golf Links Road Oakland, CA 94605