After completing Spring Migration Monitoring on June 10, the Lesser Slave Lake Bird Observatory is now well underway with the next of our core monitoring programs: Monitoring Avian Productivity and Survivorship (MAPS). MAPS studies locally breeding songbirds by capturing them at four sites in the Lesser Slave Lake Provincial Park. Currently we are banding adults or recapturing birds that we banded in previous years to estimate how many individuals are returning to breed – the survivorship part of MAPS. Later in the season, when we are banding baby birds that just left the nest, we can estimate if it was a good year for breeding attempts – the productivity part.
After we have captured, identified, and banded each bird we take several measurements. One of these measurements is to check the breeding condition. In past articles we have frequently discussed how female songbirds drop the feathers on their belly and fill under the skin with fluid to create a hot pack while incubating their eggs, but we have rarely discussed what breeding condition in a male looks like in any depth.
As you may be aware, birds are not mammals; they have several organs that are quite different from what we humans are more familiar with. If we get past the feathers, one of the starkest differences between us and most birds may be the cloaca. The cloaca is present in both males and females of most birds and reptiles and is the ‘exit point’ of their urinary, digestive, and reproductive systems. One hole for all. In contrast, us humans have a different ‘exit’ for each of these systems.
When a male is preparing to breed, hormones will kick start the production of sperm which is stored near the cloaca and causes the cloaca to appear swollen. When we part the feathers from the cloaca we can see this swelling, called the cloacal protuberance. This phenomenon was first described by ornithologists in a 1952 paper with follow up research as recent as 2012. While these cloacal protuberances are useful for telling males from females, we cannot reliably use them to track exactly where in the breeding cycle a male is because the swelling can decrease immediately after mating.
While a bird may spend days or even weeks defending a territory, finding a mate, and building a nest, the actual mating event may only last a few seconds when the male and female’s cloacae make brief contact in what is often called the “cloacal kiss”. Afterward the female develops the egg which she then lays from her own cloaca.
As our second of six MAPS periods is currently underway, we continue to see massively swollen cloacae on nearly every male bird, but soon they will shrink back down. By now, several eggs have already hatched and some early nesting species, such as Black-capped Chickadees, have even had their first set of young leave the nest and though they cannot fly well, their parents are still caring for them.
By Robyn Perkins, LSLBO Bander-in-Charge