Nest housekeeping quality genetically controlled?

[Rick H]

Over the years of monitoring martin nests it has become evident that some birds are very particular when it comes to housekeeping, while others have more important things that occupy their thinking than nest appearance. Most birds will arrange nest materials in an orderly manner within a pocket in which the eggs are laid, and some even position eggs symmetrically in a perfect circle. In contrast, some egg clutches are scattered on the bare floor of the nest compartment with essentially no fanfare. If the compartment is large enough, say 11 x 6 in, martins often separate the entrance area from the brooding area with a mud dam of variable size. Perhaps it serves to restrict predator access to the young. I have not seen a mud dam in a gourd yet. Pine straw or other plant materials like corn stalk fragments or petioles from black walnut trees form the nest matrix and in the center small leaves (e.g. crabapple) or pieces of larger ones, sometimes locust tree seed pods (¼ x 1½ in) can be found. These are used to cover the eggs before the clutch is complete and between brooding intervals when the hen leaves the nest. Unusual things like shiny foil gum wrappers, the odd 50-50 ticket stub, a small plastic toy soldier, or other material from the neighbourhood, even metal wire or string might be found.
Every year for the past three, retired bird bander-in-chief David Okines (Prince Edward Point Bird Observatory (Picton, ON), has come by around the second week of July to band martins in my backyard. Nestlings roughly 10 to 22 days old are usually the optimal age (large enough to band and less likely to fledge prematurely). Each year over 200 birds have been banded at this site. In 2025, a bird banded here Jul 10 was reported seen on Sept 10 by Adam Troyer in Conneautville, PA, just 67 mi from here directly across lake Erie and the international border. While we were banding babies I mentioned to Dave that during nest checks I have noted that eggs in some nests seemed deliberately organized with the pointy ends either inward or outward in a regular circle. In some nests it went further to the extent that the nestlings even seemed to be positionally oriented with all heads usually facing outward. However, in most others birds were randomly resting in the nest pocket. Dave was amused by this, and having a sense of science and humour, after banding babies from two different nests where nestling were ordered with heads facing outward, two of 6 babies from each nest were returned to their places in a reverse direction. In less than a minute the babies had moved back to their original position within the nests as shown in one nest in the attached photo. A random arrangement of nestlings in a third nest is also shown in the companion photo. Orderly orientation appears enduring since the attached photos were taken 4 days after banding the birds.
So it’s interesting to think that good or bad housekeeping has a genetic basis and what we might apply to explain human behaviors.

Photo credit Michelle Jacobs