The 2023 CahowCam2 star is on track to fledge around June 10th and will start its nightly excursions outside the burrow in the next few nights. During its May 30th health check, (as seen in the video below) Jeremy found that its weight and wing chord growth were progressing perfectly for a chick of its age and should reach the optimum ratios for fledging within the next few days, not to touch land again, until it returns should all go well, in 3 to 5 years!
During the nesting season, especially when food is abundant and the foraging locations are closer than usual, (as appears to be the case this year) the parents will often feed the chicks so much that their weight after feeding visits can exceed 450 grams. The chicks must then drop the excess weight, converting it to muscle and feathers to get down to an optimal range of 265-300 grams for fledging, and the parents will often abandon them in the last week to help this happen.
In parallel the chick’s wing chord length (the distance from their wrist joint to wing tip) should reach at least 255 mm. The wing growth rate of a healthy chick increases by 1cm (10mm) every 2 days, reaching the 255-275mm range just prior to fledging, which along with its weight, is used by Jeremy to track and predict the eventual fledging dates. Over the past few seasons we have found this to be quite accurate.
Also just prior to fledging, Jeremy uses bill length measurements to estimate the sex of the bird, without the need of invasive bloodwork, which when checked after they return a few years later for breeding, is proving to be 95% accurate.
Watch the LiveStreams at night over the next week, and if lucky will witness our star fledge.