Sunday was a warm, beautiful day to check on all the purple martins (all 96) The colony behind the nature center at Hammonasset currently has a combination of 125 eggs and chicks (approximately 22 chicks and 103 eggs) This colony is actually experienced 2 stressors in the last 2 years, last year the housing units needed to be moved so the new Nature Center construction could begin. Martins DO NOT like their houses moved, even a few feet. Many did not nest last year because of this. This year construction recently began in close proximity to the martin's housing. The workers are aware of the birds, but we anticipate some disruption to them despite everyone's best efforts.
The second colony at Chase Pond at Hammo currently has 166 egg/chicks.11 chicks and 155 eggs. Each colony has the same capacity for nests.
Lots of perils lie ahead for the birds, a run of cool, rainy weather can cause devastating losses. Martins need to catch flying insects to feed their young. A prolonged period of rain means no flying insects. Predators also impact the total hatch. There are predator guards to protect from snakes and ground threats but yesterday we watched the Nature Center's resident hawk circle and land very close to the martins and there are many other threats...so let's all hope for the best!
Although we begin the season by putting some nesting material in each box, it is up to the martins to add additional material and form it into their cupped shaped nest. When they are ready to lay their eggs, green leaves are added. Why they add the green leaves is a mystery. At Hammo they tend to add bayberry leaves but other martins add apple, or pear, oak or whatever seems to be available.
Bayberry leaves are highly aromatic and one of the theories is that the leaves help in pest control but the leaves may help reduce the temperature of the nest, the humidity of the nest, or help make the nest bowl easier to clean. If you want to read more about that I've included a link below.
All about the eggs - The typical martin nest has between 5-7 eggs, with 5 being the average. Subadult females lay between 3-5 eggs. The eggs are laid early in the morning over the course of several days. A cold spell can interrupt the laying process for a day or two or even limit the number of eggs in a clutch.
The incubation period for the martins is tricky to figure...the timing of the hatch begins the next to the last egg is laid and continues for 14-16 days. During this time the female transfers heat to the egg through the featherless spot on her belly called the "brood patch". This was created when hormones caused the feathers in that area to molt and the blood vessels increase. The female periodically rotates the eggs so that all areas of the eggs benefit from the warmth of this patch. Males will also sit on the eggs, but they do not help with the incubation, just help prevent heat and moisture loss and guard against predation.