This article is part of the Feathered Fridays series, a spotlight on different bird species found at your airports or aerodrome spaces.
Image: Simi @ PixaHive
Risk Level: High Risk
Overview
Cattle egrets get their names because of how often they can be seen on cattle or other large mammals like buffalo or even elephants. This dynamic can be seen as a mutualistic relationship for both the cattle and the egrets; the egrets catch any insects or small vertebrates to eat, the cattle get the relief of not having said insects and small vertebrates on their hide. Other than foraging on cattle, their favorite foods include worms, aquatic insects, frogs, fish, and small lizards.
Egret species can be difficult to differentiate as many of them look similar; white bodies, similar builds, and similar ranges. Cattle, intermediate, little, great, Chinese, and snowy egrets all have white bodies and share similar wetland habitats. Cattle egrets have short necks; they can be differentiated by other species of egrets by the size of their necks, all other species of egret have distinctive long, S-shaped necks. Another difference is color; cattle egrets are the only egret species to have orange-colored breeding plumage.
Range
Cattle egrets have two separate subspecies the western cattle egret and eastern cattle egret respectably. Western cattle egrets range from the prairie potholes in southern parts of Canada into Central and South America ranging down to southern parts of Chile and Argentina.
Eastern cattle egrets are found in most of sub-Saharan Africa, India, Southeast Asia, and Australia with some populations ranging north to parts of southern Europe to breed.
Behavior
As stated earlier, this seemingly friendly species of bird is not afraid to follow cattle, buffalo, zebra, elephants, and other large mammals. This friendly interspecies behavior translates to other bird species as well. Cattle egrets are usually fond foraging and nesting in flocks with other species of egrets like the intermediate and little egret. They are even known to nest with other species of birds like herons and cormorants.
It is rare to find a cattle egret too far from a water source. Cattle egret colonies are found along bodies of water, streams, rivers, and wetland areas. Some populations are residents all year round, while others migrate with different seasons.
In the Airfield
Airports should be mindful of animal habitats and habitat management, especially when it comes to larger flocking birds like the cattle egret that could cause serious problems if struck. Cattle egrets are attracted to grassy, flooded, mudflat areas where they forage for food like worms, insects, and frogs. Airports should stay vigilant of areas with poor drainage as they are prone to flooding and the creation of ponding areas. Another example of an airport area prone to ponding are construction sites, whether that means inside or near your airport. If your airport construction site is excavating land, those holes than turn into ponds becomes a magnet for cattle egrets to forage for food that could have been turned up. This is especially prevalent in wet climates like Southeast Asia. If your airport is in a wet climate, it can be close to impossible to manage all the waterways throughout. To prevent the presence of egrets, by not draining out a waterway, canal netting can be implemented.
When cattle egrets are spotted on the runway or near the airport, reactionary dispersal methods are commonly used. For egret and heron species, these dispersal methods include long range acoustic devices, stockwhip, pyrotechnics, and lasers. When it comes to stubborn egret species, some airports get extra creative and use dogs to chase them away.
Orlando International Airport in Florida is situated in a subcontinental wetland area making it a magnet for cattle egrets. The airport is the United States’ 12th largest and is a serious risk for egret strikes. Orlando’s airport biologists adopted a three-pronged approach that involved removing nesting habitat, oiling eggs, and increasing predators. Oiling eggs makes them nonviable; therefore, lowering the number of cattle egrets hatching each season. Increasing predators can be a risky approach, especially if they are non-native. Luckily for Orlando, raccoons are native and a man predator of cattle egret eggs. They introduced raccoons in outlying airport areas as to not release them directly in the airport to cause a raccoon problem inside the grounds. The airport biologist’s three-pronged approach led to a 75% cattle egret population decrease from 2011 to 2015.
Identifying which species of egret and bird in general can help determine a species management program.
ACRP Airportcooperative Program - Transportation Research Board. https://onlinepubs.trb.org/onlinepubs/ACRP/acrp_iop_35.pdf.
Comentarios