In the summer of 2018, I had the good fortune of watching a female Yellow Warbler build a nest, incubate her eggs and feed her nestlings. I’ve posted photos of her nest-building and nest-sitting, and now it’s time for photos of her itty-bitty hatchlings!
After June 30th, I visited the nest two more times without seeing little ones. Mrs. Yellow was still incubating her eggs on July 3rd.
On July 7th, she may have been sitting on eggs, young hatchlings or both.
W.R. Salt, in Alberta Vireos and Wood Warblers (1973), writes that the female starts incubation at least one day before she lays her last egg and the eggs hatch 10 and 11 days following clutch completion. Birds of North America online (BNA online) gives an interval of 10-13 days between the laying and hatching of the last egg in central Alberta, with a mean, mode and median of 11 days.
On June 23rd, Mrs. Yellow looked like she was finishing up nest construction. So I could guess that she laid her first egg a bit after sunrise on June 24th. Yellow warblers usually lay 4-5 eggs at 1 day intervals (BNA online), so I could continue guessing that Mrs. Yellow laid her last egg on June 27th or 28th. That would make July 8th or 9th the 11th day after clutch completion.
I didn’t “bushwack” off the forest trails to look at the eggs inside the unattended nest because I was worried the scent of my bushwacking path and the disturbed foliage would attract dangerous attention to the nest.
July 10th was my first peak at the little ones! Based on my earlier guess, this was day 12 or 13 after clutch completion, putting the likely age of the hatchlings at 1 or 2 days old. If you click on the image below to see an enlarged version, it looks like the chicks’ eyes have not opened yet. Yellow Warbler hatchling eyes open at about 3 days old (BNA online).
Hungry, hungry hatchlings! The action in the next 5 photos unfolded in less than 40 seconds!
Yay! Mommy’s got snacks!
Mommy trades the snack for a fecal sac.
I’m not sure whether Mrs. Yellow threw the fecal sac overboard or swallowed it. Supposedly, the second option is more likely (BNA online)! Then she sat on her wee ones.