Materials to the fauna and taxonomy of birds of the Iturup island based on field studies in 2004 and 2019

Ornithological studies were carried out on Iturup Island and in the adjacent sea areas during two field seasons June-July 2004 (35 days) and July-September 2019 (40 days). Line transect bird counts and ship surveys were carried out with selective collecting of specimens in working areas with aim to identify the geographical variability of island bird populations. Island biotopes were examined from the river Slavnaya in the north to the river Tikhaya in the south, coastal waters - from the northern to the southern tip of the island (with the exception of several sites on the Sea of Okhotsk side). A total of 131 bird species belonging to 16 orders and 46 families were recorded (101 species in 2004 and 110 species in 2019), expert estimates of their abundance are given. The status, distribution, and seasonal dynamics were presented for a number of species (including 16 species from the Red Books of the Russian Federation and the Sakhalin Oblast). 6 new species were added to the checklist of avifauna of the island, which totaled 244 species. These are Chinese pond heron, Ashy Minivet (single observations), Gadwall, Mandarin Duck, Green sandpiper (single observations on autumn migration), Red-crowned Crane (presumably nesting of one pair). The breeding records of Buff-bellied Pipit and the Dark-sided Flycatcher, previously considered as vagrants, were registered. The processing of collections allowed us to consider local island populations of 30 nesting species and raise the question of the possible existence of new, undescribed island races of 7 species: Spotted Nutcracker, Siberian Rubythroat, Eurasian Wren, Sakhalin Grasshopper-Warbler, Marsh Tit, Grey Bunting and, possibly Eurasian Treecreeper. The reality was also confirmed for the previously described, but not universally recognized subspecies of 5 species: Middendorff's Grasshopper-warbler, Brown-headed Thrush, Asian Brown Flycatcher, Pine Grosbeak, Rosy-cheeked Bullfinch, Coal Tit. Field studies in 2019 were carried out as part of the integrated expedition of the Russian Federation Ministry of Defense and RGO «the Eastern Bastion - Kuril Ridge».