In 2008-2023, the changes in breeding behavior of the migratory-nesting bird populations of Microcarbo pygmaeus, Nycticorax nycticorax, Ardeola ralloides, Bubulcus ibis, Egretta garzetta on biotopes were studied on the South-Western coast of the Caspian Sea. Hundreds of thousands of bird populations from Africa and South-East Asian countries migrate to the Azerbaijani sector of the South-Western part of the Caspian Sea every year. Among the above-mentioned bird species only Bubulcus ibis has a migratory-nesting population in the Gizilaghaj Bay of the Caspian Sea. The rest of the species have migratory-nesting and sedentary populations. The number of migratory-nesting populations in the study area is a hundred times more than that of sedentary populations. During this period, intra-species and inter-species competition intensifies in the struggle for nesting, feeding, roosting, resting, shelter and other living conditions between migratory-nesting and sedentary bird populations. The water level reduction and the related destruction of reeds and tamarisks, intra-species and inter-species competition lead to changes in the breeding behaviour of migratory-breeding bird populations. As a result, the continuous, sustainable reproduction of these species becomes difficult, and the adoption of new nesting places by the species makes conservation problems more urgent.