Chestnut-backed Jewel-babbler

Quick answer

Jewel-babblers were common and vocal at both of our sites, especially Kangarangate. At our higher elevation site, Munggur, where we heard and saw jewel-babblers from 1,170 to 1,655 m, all sightings were of the bicoloured (deep blue and rich chestnut) P. castanonota. At Kangarangate, most of our sightings were also of P. castanonota down to 1,000 m. However, we saw the duller, uniformly coloured P. geislerorum three times, at 1,070, 1,110 and 1,265 m: dull slate-blue individuals that were presumed males, and dull brown individuals presumed to be females. Calls of the two species seemed similar: paired notes, tsp‐tsp, the secondȱofȱeachȱpairȱlouder; ȱandȱaȱseriesȱofȱnotesȱonȱtheȱsameȱhighȱpitch, ȱtheȱfirstȱnotesȱshort, ȱ thenȱaȱlongȱnote, ȱandȱfinallyȱtheȱloudȱ tsp‐tsp. Gilliard collected both species in the Adelberts atȱ differentȱ sitesȱ butȱ similarȱ elevationsȱ (Gilliardȱ & ȱ LeCroyȱ 1967: ȱ 66), ȱ asȱ didȱ Stevensȱ inȱ theȱ Herzog Mts. (Greenway 1935: 55). Coates (1990: 66) found both species co-existing in the Adelberts, even on adjacent territories, at 800 – 1,220 m. The ecological relations between these species remain mysterious to us, because the other four co-existing species of Ptilorrhoa (P. castanonota, ȱSpottedȱ P. leucosticta, Blue P. caerulescens and Black-vented Jewel-babblers P. nigricrissus) segregate cleanly by elevation (Diamond et al. 2019: 455 – 456). P. geislerorum wasȱbelievedȱtoȱbeȱconfinedȱtoȱtheȱnorthernȱwatershedȱofȱsouth-eastȱNewȱGuineaȱwestȱtoȱtheȱ Adelberts, ȱuntilȱVerhelstȱ & ȱPottierȱ (2020) ȱsurprisinglyȱdiscoveredȱ P. geislerorum or a similar taxon sharing Yapen Island with P. castanonota.