Stuart Rae

Evidence of polygamy in the Tawny Frogmouth

An adult male Tawny Frogmouth sits second from the right between five fledglings. 

I recently found a brood of five fledgling Tawny Frogmouths Podargus strigoides that were being attended by one adult male and two adult females. The birds were first observed at the nest on 14 November 2024 and the birds were seen on several subsequent visits to the nest area (up to 29 Dec 2024). The nesting area was in dry sclerophyll forest on Black Mountain in the Australian Capital Territory (ACT). As far as I can determine, this is the first record of a brood of five Tawny Frogmouths.

The two adult female Tawny Frogmouths, perched on the same branch on 29 November. Female A is at the top of the branch, female B lower down on the same branch.

The observations were made while monitoring nests and broods as part of a long term study of Tawny Frogmouth breeding ecology (18 years). Six trios of breeding Tawny Frogmouths have been recorded previously in the study, although none with more than three fledglings (1x1, 2x2, 2x3, 1x failed). These records have not been published, I had planned to publish them in more context when all the data are collected. However, due to the interest in this new record, I decided to write a brief report that was published in the local bird club journal, Canberra Bird Notes 49(2) see here.  It is not known if one or both females laid the eggs in the nest in this instance. Given that frogmouths usually lay 1-3 eggs it appears that both females in this instance laid eggs and this was a polygamous relationship consisting of a breeding trio. In the article, I pondered whether this was the first record of a brood of five or of polygyny in any frogmouth species, or polygyny in any of the Caprimulgiformes. The records for the frogmouths seem to be the first of their kind, although there have been previous records of polygyny in nightjar species. 

          

Above left: Female A. She is overall more grey than female B. There is less rufous colouring around the face and less prominent streaks on the breast. 

Above right: Female B. She is overall more rufous, especially on the wing coverts and around the face. Her breast is more obviously streaked.

The breeding biology of the Caprimulgiformes is poorly known and they are generally thought to be monogamous (Cleere 2010). Polygyny has seemingly only been documented in four species, the Standard-winged Nightjar Macrodipteryx longipennis (Holyoak 2001), the Pennant-winged Nightjar M. vexillarius (Jackson 2004), the White-winged Nightjar Caprimulgus candicans (Pople 2003), and European Nightjar Caprimulgus europaeus (Odder Jensen 2013, Evens et al, 2024). The males of the first two species have exaggerated plumage differences from the females, such as elongated feathers, which they use for display in leks and so are considered to be polygynous. Male White-winged Nightjar also display in dispersed (exploded) leks (Frith 2024) and have been proved to mate with more than one female in a study using VHF radio tracking. The European Nightjar has only recently been proved to be polygynous in studies using GPS-telemetry.

A full report will be published on the breeding ecology of Tawny Frogmouths in the ACT when the study is completed and a separate publication will discuss polygyny in the species and other Caprimulgiformes.

The adult male frogmouth sits with four of the fledglings behind him, on 29 December. The other fledgling was with female A and female B was on a branch above them.

Cleere, N. & Nurney, D. (1998). Nightjars. – Pica Press, Sussex

Evens, R., Lathouwers, M., Creemers, J., Ulenaers, E., Eens, M., & Kempenaers, B. (2024). A Case of Facultative Polygyny in an Enigmatic Monogamous Species, the European Nightjar (Caprimulgus europaeus). Ecology and Evolution, 14(10): e70366.

Frith, C. B. (2024). Use and definitions of the terms arena, lek and court in describing avian courtship sites. Ibis.

Holyoak, D.T. (2001): Nightjars and their allies: The Caprimulgiformes. – Oxford University Press

Odder Jensen, N. (2013). A Case of Polyterritorial Polygyny in European Nightjar Caprimulgus europaeus. Dansk Ornitologisk Forenings Tidsskrift 107: 239–244.

Jackson, H. D. (2004). Courtship displays of the Pennant-winged Nightjar, Semeiophorus vexillarius. Ostrich 75: 1-4.

Pople, R. G. (2003). The ecology and conservation of the white-winged nightjar Caprimulgus candicans [Apollo - University of Cambridge Repository]. https://doi.org/10.17863/CAM.16393