CHESTNUT-BACKED JEWEL-BABBLER Ptilorrhoa castanonota and DIMORPHIC JEWEL-BABBLER P. geislerorum

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 LeCroyȱ1967: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 .