Open-cup songbird nests, like the one occupied by these catbirds, can be absolute marvels of weaving intricacy, but they’re still exposed to the elements. Gray Catbirds typically choose dense shrubs that both conceal the nest from predators and provide some degree of shelter. But when extremes come along—such as hot temperatures and direct sun or windstorms and heavy rain—the adults will do their best to cover the helpless chicks. This is especially important because the nestlings have not yet developed the contour and flight feathers that adults keep waterproof with preen oil.
On this particular afternoon a huge system of thunderstorms moved in. This was only mid-afternoon, but as you can see from the second video the clouds blocked almost all light. Buckets of rain poured down and lightning flashed all around, giving me a great opportunity to see this excellent parent sheltering the nestlings through the weather (make sure your sound is on for the full effect!).
On July 21, the second egg in the nest hatched!! Songbirds are altricial, meaning they’re helpless when they hatch and require parental care in the nest (contrasting with precocial birds, like shorebirds, that are relatively mature and can start running around soon after hatching). As you can see, the helpless nestlings’ eyes are still covered and they’re mostly naked, so they still require brooding from the adult to maintain stable temperature. Meanwhile, the adults also have to bring small prey items to the nestlings. But with all the brooding these feeding trips aren’t too frequent yet.
According to the Cornell Lab of Ornithology, during these early days the male does most of the feeding (I think the female deserves a break, don’t you?). These tiny beakloads with lots of time brooding in between may not seem like much, but providing protein-packed little invertebrates like grubs and arthropods can grow these little chicks quickly, as you’ll see!
Gray Catbird incubation lasts about 12 days. During that time, this mom was brave and vigilant. As this was right outside our front door (and we don’t have the luxury of alternative exits) I knew she’d be dealing with our comings and goings throughout this whole breeding ordeal. Since the shrub had been recently trimmed, I was lucky that at one point while walking past you could see straight through a gap to see her quietly watching you.
Embryos require a fairly stable and narrow temperature range, so her vigilance is important. Carryover effects of suboptimal temperatures during incubation range from slower nestling growth (Ospina et al. 2018, Ecol Evol) to more fearful behaviors in the offspring (Bertin et al. 2018, Scientific Reports). In catbirds, the female does all the incubating and will typically sneak off to eat around sunrise. I never directly saw the male coming to feed the female on the nest during the day, but that behavior is also typical for these songbirds.
On July 20, we had our first nestling! (It was only 8 days after I first noticed the eggs, so the first must have been laid a few days earlier as it usually takes about 12 days to hatch.) It doesn’t immediately start begging for food, so if you listen in the video you can hear the adult give several “quirt” calls that eventually trigger the open-mouthed begging response.