I was watching some Short-tailed Babblers (Pellorneum malaccense) on 28th April 2022 at a mixed primary-secondary forest location at the outskirts of Ipoh when this Black-capped Babbler (Pellorneum capistratum nigrocapitatum) walked out of the undergrowth. What was unexpected was the faecal sac it was carrying. I am used to nesting birds either eating the faecal sac of their juveniles or disposing of it some distance away from the nest. But this bird’s behaviour (and demeanour) appeared to be purposefully taking the faecal sac somewhere rather than removing or disposing of it. The bird was surprised to see me but after a brief pause, it carried on its way and disappeared into the undergrowth further down, still carrying the faecal sac.
I could just be mistaken and the bird is just nesting and this is the ‘conventional’ faecal sac removal. But it got me thinking – do birds of one species eat the faecal sacs of another species? Do birds of one species collect faecal sacs of another species and feed them to their offspring? Especially as we know that the faecal sacs of younger juveniles contain undigested food that may be nutritious.
There are reports of brood parasites like the Brown-headed Cowbirds (Molothrus ater), which do not care for their own offspring, eating the faecal sacs of nestlings of their host species (Stake, Cavanagh 2001).
I would appreciate any opinions.
Stake, M. M.; Cavanagh, P. M. (2001). “Removal of Host Nestlings and Fecal Sacs by Brown-headed Cowbirds”. The Wilson Bulletin. 113 (4): 456–459.
Dato’ Dr Amar-Singh HSS – Ipoh, Perak, Malaysia