The Underbelly of a Rookery

You can often discern the sounds of a wading bird rookery before it comes into view. It is an auditory landscape that is often unseen. This season I want to dive into the underbelly of our local rookeries to listen and observe and learn more about the activity and behaviors of wading birds where they breed and nest.

Here are some of the sounds you might hear:

1. Calls and Vocalizations: Wading birds are known for their distinctive calls, which vary from species to species. You may hear the deep, guttural calls of great blue herons, the throaty squawks of snowy egrets, or the melodious trills of little blue herons. These calls serve various purposes, including communication between mates, signaling territorial boundaries, and coordinating nesting activities.

2. Wing Beats: As wading birds come and go from the rookery, the rhythmic beat of their wings creates a soft, whooshing sound. This sound can be particularly pronounced during periods of high activity, such as when birds are returning to their nests with nesting material or food for their young.

3. Rustling of Feathers: Wading birds are often seen preening and grooming their feathers, and the rustling of feathers against each other is a common sound at a rookery. This gentle sound adds to the overall ambiance of the rookery and is a sign of the birds' meticulous care for their plumage.

4. Nesting Activity: The construction and maintenance of nests by wading birds can also generate sound. You may hear the sharp snapping of twigs as birds gather materials for their nests, as well as the soft thuds as they arrange these materials into shape.

5. Interactions Between Birds: At a wading bird rookery, interactions between birds are frequent and varied. You may hear the soft clacking of bills as birds engage in courtship displays or the squabbling that signifies territorial disputes, as well as the occasional splash as birds take off or land in the water surrounding the rookery.

The birds that I observed at four rookeries on the coast of South Carolina included:

• Black-crowned Night Heron

• Great Egret

• Green Heron

• Little Blue Heron

• Snowy Egret

• Tricolored Heron

• Wood Stork

• Yellow-crowned Night Heron

• Anhinga

In addition, boat-tailed grackles often build their nests in dense vegetation close to water sources. They may construct their nests in tall grasses, low shrubs, or reed beds, providing them with protection from predators and easy access to food. It's not uncommon to find boat-tailed grackle nests in areas where wading birds like egrets and herons also nest, as they share similar habitat preferences near wetlands and marshy areas.

Most rookeries are located small islands on freshwater ponds where water-loving trees like willows grow and alligators are present. According the South Carolina Department of Natural Resources: Many species of wading birds, including wood storks, nest in vegetation over open water. Colonial wading birds are susceptible to predation by terrestrial predators such as raccoons. Alligators protect nesting wading birds by deterring raccoons from accessing nests. When aquatic vegetation becomes too thick, raccoons are able to access the nests and depredate eggs and chicks. Upon further investigation, I read several studies about site selection and the presence of alligators. Collectively, these findings bolster the theory that wading birds selectively opt for nesting sites shielded from predators, influenced by insights from both fellow species and alligators. Moreover, they imply that the core mechanism driving this habitat selection stems largely from the protective advantages inadvertently offered by alligators!

From the abstract of Attraction of Nesting Wading Birds to Alligators (Alligator mississippiensis). Testing the ‘Nest Protector’ Hypothesis". :

Ecological facilitation (mutualism and commensalism) appears to be a strong force shaping biotic communities, and may be more likely in stressful and dynamic environments like wetlands. We examined a specific type of mutualism, ‘protective nesting associations,’ between herons and egrets (Ardeidae) and American alligators (Alligator mississippiensis). We predicted that wading birds would be attracted to sites with alligators. A survey of potential nesting sites in the Everglades showed strong nonrandom association, with wading birds never nesting without alligators. At previously unoccupied nesting colony sites, we experimentally manipulated apparent densities of alligators and birds using alligator and bird decoys. Small day-herons (little blue herons (Egretta caerulea), tricolored herons (Egretta tricolor), and snowy egrets (Egretta thula)) were significantly more numerous at sites with both alligator and bird decoys than other treatments. These findings together support the hypothesis that wading birds actively choose predator-protected nesting locations based in part on information from both conspecifics and alligators, and suggest that the mechanism supporting this habitat choice is primarily due to nest protection benefits the alligators inadvertently provide. We propose that this interaction is strong and could be geographically widespread, and suggest that it may be critical to shaping management and conservation of wetland function.

Understanding the dynamics of a wading bird rookery, including the cohabitation with other bird species and the protective role of alligators, can make someone a better bird photographer in several ways. Firstly, being aware of the sounds and activities within the rookery can help photographers anticipate and capture unique moments, such as interactions between different bird species or the swooping of alligators. Secondly, knowing the nesting habits and preferred habitats of wading birds allows photographers to position themselves strategically for optimal shots while respecting the birds' natural behavior and safety. Finally, understanding the role of alligators in providing unintentional protection to the rookery can inform photographers about potential hazards and safety precautions when navigating the area for photography. Overall, this knowledge enhances a photographer's ability to capture compelling and ethically responsible images of wading birds and their habitat.