A total of 365 species were included in the first list of the bird fauna of the Danube Delta Biosphere Reserve (DDBR) (Marinov et al. 2023). Not even two years after publication, new species were identified. The new list also included species recorded before 2023 but omitted from the article mentioned above. Initially, we intended to prepare only a corrigendum, but considering that eight new species were included, we decided to return with a new article. In the future, we plan to create an official online list of birds from the DDBR, given that the list will continue to grow due to the increasing number of ornithologists and bird-watchers who come to ring and observe birds.

As mentioned in the first Danube Delta Biosphere Reserve bird checklist (Marinov et al. 2023), research on this subject began in 2003 and has continued to the present. In addition to our observations, we referred to specialized literature, especially sources providing information on numerical ratings or rare alerts (Ion 2009; Kiss 1973, 1982a, 1982b; Kiss and Szabó 2000, 2003; Maarten et al. 2004; Munteanu 1960, 1976, 1977, 2006, 2009; Munteanu et al. 1989; Munteanu and Toniuc 1991; Munteanu et al. 1991, 1996, 2002, 2004; Munteanu and Marinov 2004; Munteanu and Weber 2005; Sándor et al. 2007). At the same time, we used information from the Rombird website (https://rombird.ro/). The use of Rombird data was requested in writing on 15 January 2025 via email, and the agreement to use these data for the publication of a scientific article was confirmed by a positive written response on 27 February 2025. The study area comprises the entire territory of the Danube Delta Biosphere Reserve.

In the previous list (Marinov et al. 2023), seven species were excluded: Syrrhaptes paradoxus, Columba livia forma domestica, Streptopelia orientalis, and four species that escaped from households or private collections: Cygnus atratus, Alopochen aegyptiacus, Aix galericulata, and Aix sponsa. In the current list, as mentioned above, eight new bird species were added for the Danube Delta Biosphere Reserve. These eight species are, in taxonomic order, Calidris subruficollis, Clamator glandarius, Anthus petrosus, Phylloscopus bonelli, Phylloscopus schwarzi, Bucanetes githagineus, Emberiza pusilla, and Seiurus aurocapilla (Table 1). Without a doubt, the last species, the ovenbird (Seiurus aurocapilla), is particularly important, as it led to an increase in the number of bird families in the DDBR from 60 to 61 (Parulidae). Several other species were also analyzed, such as the Armenian gull (Larus armenicus) and the desert wheatear (Oenanthe deserti), but these were identified just outside the DDBR limits. A special case is represented by Numenius tenuirostris, which was the subject of a recent study in which modeling suggested a 96% probability of extinction (Buchanan et al. 2024). However, the IUCN still classifies this species as critically endangered, and on this basis, we have not removed it from our list (BirdLife International 2018).

Given that all eight newly registered species are accidental, they are not supported by scientific articles documenting their presence in the DDBR; available information is limited to press articles and online sources. Unlike the first list (Marinov et al. 2023), we therefore did not include qualitative and quantitative indices or bibliographic resources in Table 1. For qualitative and quantitative indices derived from the Standard Data Forms of the two SPA Natura 2000 sites overlapping with the DDBR (ROSPA0031 Danube Delta and Razim Complex–Sinoie and ROSPA0076 Black Sea), as well as those added by us where missing, together with the related bibliography, consultation of the first list is recommended (Marinov et al. 2023).

The 373 bird species recorded in the DDBR belong to 61 families (out of a total of 65 families in Romania) and 19 orders (out of 19 orders in Romania; Table 1). In this analysis, and in Table 1, we followed the systematics proposed by Munteanu (2001), the most recent comprehensive nomenclatural reference for the ornithofauna of Romania.

The number of bird species recorded in the Danube Delta Biosphere Reserve increased over the last two decades by 13%, from 325 to 373. This increase is determined by the growing interest in birdwatching, improved equipment performance, and increased funding for monitoring projects. The large number of bird species highlights the importance of the Danube Delta for birds and the need for protection of both the Danube Delta and its ornithofauna.