Our paper on how tree swallow females adjust parental effort and what role glucocorticoid hormones play in this has been published at Royal Society Open Science. The open access paper can be accessed here. We used an automated playback device (see the description here) consisting of an RFID reader and and a Raspberry PI computer to play extra nestling begging calls to the females (but not the males) every time they visited the nest for six hours. The females ended up upping their parental effort for only about the first two hours of the playback duration. We also obtained blood samples to look at corticosterone (cort) levels of females after the playback with the expectation that if the females increase their parental effort and if cort is involved in this adjustment, we should see higher cort levels in females that received the playbacks compared to controls. We did not find such a difference in cort levels, possibly because the effect of playbacks on feeding rates was transient and confined only to the first two hours of playback. It therefore remains an open possibility that cort is involved in some way in the strategic adjustment of parental care.