Branta Issues > Issue №7 (2004)

Dynamics of species composition and numbers of Ciconiiformes birds in the north near Azov area (1988-2004).

Koshelev A.I., Koshelev V.A., Peresad’ko L.V.

The  paper  presents  the  results  of  studying  colonies  and  number  dynamics  of herons  in  the  north  near Azov  area for  1988-2000.  There  are  9  species  of Ardeidae  in  the region.  Of them  8 species  breed,  and another Cattle Egret is  a  rare  bird o f  passage.  Six species  rnnter  in  the  region. Total numbers  of herons for a  breeding period  in wet seasons  reach  3,860-4200  pairs,  while  in  dry  years  these numbers dropped to 2,400  -  2,500 pairs.  Twenty-four locations o f  colonies and settlements of Ciconiiformes are found in  the  region,  and  75%  o f  them  are mixed.  Large stable perennial settlements  that  consist  of  2-26  colonies  develop  in  reed plavni  of  upper Molochnyy Liman,  in  arboreal-shrubby  vegetation  of  islands  Bol'shiye  Kuchugury  and  Malye Сuchugury,  on  Bol'shoy  Islands  of Obitochnyy  Bay,  and  in  wet  years  in  reed plavni  of middle Molochnaya  River.  Small colonies of arboreal and reed types are  not constant,  but dynamic  in  time  and space.  Among  breeding species  Grey Heron  and  Great  White  Egret dominate;  their  numbers  in  three  settlements for  various  years  were  500-1,500  and 200-450 pairs  relatively.  In  wet  years  there  usually  develop  shallow pools  in  which  birds forage,  and  numbers  of small  species  of herons  increase  while  in  dry  years  their  numbers depressed. According to  a type  of the  water body  and habitat  herons form  colonies  of different  types:  arboreal, reed  and  terrestrial.  The  type  of breeding  (single-territorial,  in groups or colonial)  reflexes flexible  strategy  of birds  and  is  determined by  ecological conditions  of the  season.  Colonies  of reed  type  dominate  (60%).  They  differ from  arboreal colonies by  their short  life  and every year dislocation  within  one water body  or on  neighboring  bodies.  Depending  on  ecological  conditions  birds  can  both  change  location  of  the colony,  and  also  its  type from  reed  to  arboreal or  terrestrial  and  vise  versa  either during a  season  or  in  different  years.  Average  size  o f  a  mixed  colony  is 33.3-116.3  nests  in  different years,  monospecies  colonies  contain  35-65 pairs.

Spatial pattern  of colonies of  reed type  is simpler in  comparison with  that of tree  type.  The stratification  in  a  nest  location  is  low  or absent,  the  horizontal pattern  is  determined  by characteristics and mosaic of reedbeds. Nests of one species are mainly distributed in  compact groups  that  isolated from  analogical  nest groups  of other heron  species.  Grey Heron and Great  White Egret are  the most plastic  species  in  choosing breeding places.  They  are high-tolerated  to  disturbance.  Prohibition  to  shoot herons,  development of the  net of natural  reserve  areas provided  restoration  o f  their numbers  in  the  south  of Ukraine  including the  north  near Azov  area  and favour further  increase  in  particular for  large piscivorous species.  Discovering  and protection  o f  new  colonies  of Ciconiiformes  and places  of their mass  concentration  in post-breeding period will  contribute  to  their successful existence.