Check out the spectacular images of the Grey-rumped Treeswift (Hemiprocne longipennis) nesting in an earlier post HERE. In this post, Jeremiah Looi’s series of video clips focuses on the different shift changes when one adult leaves the nest to give way to another to take over the incubation of the egg.
The above clip shows the female incubating the single egg. She is recognised by her blackish ear-coverts as compared to the male’s prominent rufous ear-coverts. She is restless, calling softly, as her mate is around. Suddenly she raises her wings and her mate arrives by her side. She flies off, dropping backwards and downwards so as not to displace the egg by her sudden departure. The male slides sideways to take her place in the nest.
In the clip above, the male is incubating the egg and calling softly. Note that his wing tips are crossing over the forked tail, a characteristic feature of the species. Suddenly he flies off, again dropping backwards and downwards. Within seconds the female flies up from below to take over the incubation. Note her forked tail moving against the crossed wing tips as she settles down. She moves closer to the nest so that her brood patch is in direct contact with the egg. The egg is barely visible at the moment of shift change.
The above clip gives a back view of the pair of treeswifts as they undergo a shift change. The female on the left is on nest. As she flies off, the male immediately moves sideways to fill her space. He moves his head around constantly, obviously not comfortable with the excited photographers below
There are times when the nest is left unguarded, without any adult incubating the egg, as seen above. The frailness and delicate nature of the nest, stuck precariously to the side of the branch is then open to scrutiny.
An earlier post gives more information on the nesting behaviour of this Grey-rumped Treeswift, including how often the birds change shifts during egg incubation LINK.