1. The Concept of Bird Species: Theory and Practice

   • E. A. Koblik
   • Ya. A. Red’kin
   • A. A. Mosalov

   OriginalPaper 13 January 2021 Pages: 707 - 723

   

2. Differential Migration of Birds: Diversity and Inconsistency

   • V. A. Payevsky

   OriginalPaper 13 January 2021 Pages: 724 - 734

3. Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre 1984) from Vietnam

   • K. I. Prokina
   • L. V. Radaykina
   • A. P. Mylnikov

   OriginalPaper 13 January 2021 Pages: 735 - 746

   

4. Parasites of Common (Sterna hirundo) and Arctic (Sterna paradisaea) Terns (Charadriiformes, Laridae) in Karelia

   • D. I. Lebedeva
   • G. A. Yakovleva
   • A. V. Artem’ev

   OriginalPaper 13 January 2021 Pages: 747 - 752

5. A New Glance at Old Samples: Remains of Freshwater Invertebrates Associated with Mummified Carcasses of Large Quaternary Mammals

   • A. A. Kotov
   • A. N. Neretina
   • F. K. Shidlovskiy

   OriginalPaper 13 January 2021 Pages: 753 - 761

   

6. Cucumaria fedotovi, a New Species of Holothurian (Holothuroidea, Dendrochirotida, Cucumariidae) from the Karaginskii Gulf, Bering Sea

   • E. G. Panina
   • V. G. Stepanov
   • A. V. Martynov

   OriginalPaper 13 January 2021 Pages: 762 - 770

   

7. Rational (Sustainable) Use of Waterfowl Resources: Demographic Status of the Population and Harvest Rates

   • S. P. Kharitonov

   OriginalPaper 13 January 2021 Pages: 771 - 781

   

8. Variability of the mtDNA Control Region in the Bean Goose, Anser fabalis Latham 1787, in the Russian Far East

   • D. V. Volkovsky
   • P. V. Fisenko
   • Yu. N. Zhuravlev

   OriginalPaper 13 January 2021 Pages: 782 - 790

   

9. Dynamics of the Onset of White-Tailed Eagle (Haliaeetus albicilla) Breeding in the Central Part of the Volga–Kama Region and Possible Explanations

   • R. Kh. Bekmansurov

   OriginalPaper 13 January 2021 Pages: 791 - 800

   

10. The Singing Behaviour of the Long-Tailed Shrike (Lanius schach erythronotus)

    • A. S. Opaev

    OriginalPaper 13 January 2021 Pages: 801 - 806

    

11. Association of Success in Interspecific Rearing of Nestlings with the Width of Trophic Niche of the Recipient Species in Hollow-Nesting Birds

    • T. A. Ilyina
    • A. V. Krupitsky
    • A. V. Bushuev

    OriginalPaper 13 January 2021 Pages: 807 - 820

    

12. Egg Size as the Main Stimulus to Discriminatory Behavior of the Yellow-Browed Warbler (Phylloscopus inornatus, Phylloscopidae) under Brood Parasitism of the Oriental Cuckoo (Cuculus optatus, Cuculidae)

    • S. G. Meshcheryagina
    • G. N. Bachurin
    • M. G. Golovatin

    OriginalPaper 13 January 2021 Pages: 821 - 835

    

13. Evaluating the Capability of Mirror Self-Recognition in Hooded Crows (Corvus cornix)

    • A. A. Smirnova
    • Yu. A. Kalashnikova
    • Z. A. Zorina

    OriginalPaper 13 January 2021 Pages: 836 - 843

    

14. Population Dynamics of the Common Shrew (Sorex araneus) (Experience in an Analytical Review of the State of the Problem)

    • E. V. Ivanter

    OriginalPaper 13 January 2021 Pages: 844 - 853

15. Evolution and Morphological Variability of Cheek Teeth in the Kudaro Cave Bear (Ursus kudarensis, Carnivora, Ursidae)

    • G. F. Baryshnikov
    • A. Y. Puzachenko

    OriginalPaper 13 January 2021 Pages: 854 - 877

    

16. Implications of the Discovery of a Stag Moose (Cervalces sp., Cervidae) Skull with Antler Beams of Different Lengths

    • P. A. Nikolskiy
    • A. E. Basilyan
    • V. V. Pitulko

    OriginalPaper 13 January 2021 Pages: 878 - 885