ОСОБЕННОСТИ ГНЕЗДОВЫХ ПОСТРОЕК СЕРОГО ЖУРАВЛЯ GRUS GRUS В КОНТЕКСТЕ РАЗНООБРАЗИЯ ГНЁЗД ПАЛЕАРКТИЧЕСКИХ ЖУРАВЛЕЙ

• Main Authors: ВИНТЕР СЕРГЕЙ ВЛАДИМИРОВИЧ, ГОРЛОВ ПЁТР ИВАНОВИЧ, ШЕВЦОВ АНАТОЛИЙ АЛЕКСЕЕВИЧ, АНДРЮЩЕНКО ЮРИЙ АЛЕКСЕЕВИЧ
• Format: Text
• Language: unknown
• Published: Русский орнитологический журнал 2016
• Subjects: Tundra; midnight sun
• Online Access: http://cyberleninka.ru/article/n/osobennosti-gnezdovyh-postroek-serogo-zhuravlya-grus-grus-v-kontekste-raznoobraziya-gnyozd-palearkticheskih-zhuravley; http://cyberleninka.ru/article_covers/16900256.png

Classification of nest constructions and parameters of their unified measurements are proposed on the basis of 35-year observations of nesting cranes in various regions of the former USSR and modern Ukraine (447 Grus nests and 111 Anthropoides nests). This classification allows comparing the measurements of the nests of the same types and usage of the frequencies of the various types of nests for comparison of the settlements in different locations of breeding ranges. Two types of nest constructions were distinguished for seven species of Palearctic cranes: 1) Anthropoides -like, or “the nest on the tree stem base” (99.5% of demoiselle cranes Anthropoides virgo, 85.0% of the lesser sandhill cranes Grus c. canadensis, 10.0 to 15.0% of steppe common cranes G. g. grus on the left bank of the Dnieper River in Ukraine); and 2) Grus -like, or “the nest on the water” (0.5% of demoiselle cranes, 10.0 to 15.0% of the lesser sandhill cranes, 59.0 to 71.0% of steppe common cranes in Left-bank Ukraine, all red-crowned cranes G. japonensis montignesia, white-naped cranes G. vipio, hooded cranes G. monacha, and Siberian cranes G. leucogeranus). The following functionally different nest constructions were distinguished among 414 nests found on three permanent study plots in Left-bank Ukraine in accordance to their placement: I. Nests for clutches three types of constructions with almost no transitional types: 1. “On the water” ( Grus -like type, 59 to 71% of nests). A large flat platform with a faint hollow made of the puddled last year’s and green grass, sometimes with dry tree branches, constructed in the shallow water, often encircled by water lacking any vegetation, which had been pulled out by cranes. 2. “At the tree stem base” (2 to 13% of nests). This type is transitional to the next one; a part of the nest was placed on relatively gently-sloped ground patch at the alder stem base (or on ground islets with trees, or without them in the flooded alder forest), whereas a more bulky part was “stretched out” over the water. 3. “On the tree stem base” ( Anthropoides -like type, 16 to 36% of nests). The nest was placed on ground islets on alder or birch stem bases (or without trees); the lining was “formal” (playing no heat-insulating role in contradistinction to nests of the two previous types), made mostly of green grass (if available nearby), or alder and birch twigs. In some cases, nests of this type lacked any lining, and the remains of tree twigs and branches in them just prevented the eggs being rotated by adults from rolling out of the nests. II. “Training” nests with no clutches constructed by the nesting cranes or by non-breeding territorial birds. These constructions were of the same types as the nests containing clutches; their proportions in three locations of the range were similar. Peculiar traits of the substrate in these three locations were shown to “permit” various proportions of different types of the nests. A non-breeding territorial pair constructed 2.0 nests on average, whereas the average number of nests built by a breeding pair was 1.59. III. “Heating” and “night” nests constructed by adults when their chicks were younger than two weeks. They usually looked like “ground islets” with trampled grass in alder forests and were constructed up to 50-120 m away from the nests with clutches. IV. “Nurseries” arranged by parents in the period when their chicks were younger than two weeks were found near 46.5% of nests. Adult cranes intentionally changed their chicks’ environment, which could increase the young birds’ chances for survival. The parents took a tuft of Carex riparia, Scirpus lacustris, or Typha latifolia, but did not tear it off and just placed it on the water surface. They arranged a kind of “grass carpet” for the chick, so it did not have to swim. The chick didn’t lose energy to move across the plots overgrown with tall sedge when it followed the adults. When in danger, it “plunged” from the “nursery” into tall sedge and hided there. The hatching process lasted for 44 days (10 seasons on three permanent study plots), whereas “nurseries” were found there only during 16 days, in the period between 4 and 20 May. The median date of hatching was 11 May (120 out of 228 nests); the median date of registration of “nurseries” fell on 12 May, i.e., a day later. Over 9 seasons, 76 “nurseries” were found near 34 (100.0%) nests (22 pairs) on three permanent study plots. The number of “nurseries” within the nesting territory of a pair was different. Thirteen nests (38.3%) had only one “nursery” nearby; two “nurseries” were found near 8 nests (23.5%), three near 6 nests (17.6%), four near 5 nests (14.7%), and 2 nests (5.9%) had 5 “nurseries” each. Three pairs out of 22 had “nurseries” in three different seasons. The majority of “nurseries” (92.2%) were located close to the nests or no farther than 40 m away from them; only 7.8% of “nurseries” were constructed at a distance of 40 to 150 m from the nests. Peculiar traits of nest constructions of “true cranes” could be probably used in taxonomy. Their diversity within a small group (7 Palearctic species of 2 genera) is noteworthy. Demoiselle cranes place their nests on dry flat elevations, as close to the sources of drinking water (including those of anthropogenic origin) as possible. The lesser sandhill cranes construct nests on hillocky tundra with abundant water bodies of different types; they evidently do not use these water bodies as defensive barriers against predators, because of the polar day and a wide view of the terrain. Placement of the nests by Siberian cranes must be determined by the dominating landscape of the habitats, wide view of the vicinities, and the absence of predators rather than by the polar day. Finally, white-naped, red-crowned, common, and hooded cranes inhabiting regions lacking midnight sun (and for the latter two species tree vegetation often interferes with the wide view) construct nests exclusively in the shallow parts of different water bodies. In the darkness, it allows them to hear the approaching predator in advance. Thus, a certain species-specific dependence of cranes nest constructions on the type of substrate in the nesting habitats indicates high ecological flexibility of Gruidae that allowed the family to colonize almost the entire Palearctic. The data reported here might of importance for research on taxonomy of cranes as well. Classification of nest constructions and parameters of their unified measurements are proposed on the basis of 35-year observations of nesting cranes in various regions of the former USSR and modern Ukraine (447 Grus nests and 111 Anthropoides nests). This classification allows comparing the measurements of the nests of the same types and usage of the frequencies of the various types of nests for comparison of the settlements in different locations of breeding ranges. Two types of nest constructions were distinguished for seven species of Palearctic cranes: 1) Anthropoides -like, or “the nest on the tree stem base” (99.5% of demoiselle cranes Anthropoides virgo, 85.0% of the lesser sandhill cranes Grus c. canadensis, 10.0 to 15.0% of steppe common cranes G. g. grus on the left bank of the Dnieper River in Ukraine); and 2) Grus -like, or “the nest on the water” (0.5% of demoiselle cranes, 10.0 to 15.0% of the lesser sandhill cranes, 59.0 to 71.0% of steppe common cranes in Left-bank Ukraine, all red-crowned cranes G. japonensis montignesia, white-naped cranes G. vipio, hooded cranes G. monacha, and Siberian cranes G. leucogeranus). The following functionally different nest constructions were distinguished among 414 nests found on three permanent study plots in Left-bank Ukraine in accordance to their placement: I. Nests for clutches three types of constructions with almost no transitional types: 1. “On the water” ( Grus -like type, 59 to 71% of nests). A large flat platform with a faint hollow made of the puddled last year’s and green grass, sometimes with dry tree branches, constructed in the shallow water, often encircled by water lacking any vegetation, which had been pulled out by cranes. 2. “At the tree stem base” (2 to 13% of nests). This type is transitional to the next one; a part of the nest was placed on relatively gently-sloped ground patch at the alder stem base (or on ground islets with trees, or without them in the flooded alder forest), whereas a more bulky part was “stretched out” over the water. 3. “On the tree stem base” ( Anthropoides -like type, 16 to 36% of nests). The nest was placed on ground islets on alder or birch stem bases (or without trees); the lining was “formal” (playing no heat-insulating role in contradistinction to nests of the two previous types), made mostly of green grass (if available nearby), or alder and birch twigs. In some cases, nests of this type lacked any lining, and the remains of tree twigs and branches in them just prevented the eggs being rotated by adults from rolling out of the nests. II. “Training” nests with no clutches constructed by the nesting cranes or by non-breeding territorial birds. These constructions were of the same types as the nests containing clutches; their proportions in three locations of the range were similar. Peculiar traits of the substrate in these three locations were shown to “permit” various proportions of different types of the nests. A non-breeding territorial pair constructed 2.0 nests on average, whereas the average number of nests built by a breeding pair was 1.59. III. “Heating” and “night” nests constructed by adults when their chicks were younger than two weeks. They usually looked like “ground islets” with trampled grass in alder forests and were constructed up to 50-120 m away from the nests with clutches. IV. “Nurseries” arranged by parents in the period when their chicks were younger than two weeks were found near 46.5% of nests. Adult cranes intentionally changed their chicks’ environment, which could increase the young birds’ chances for survival. The parents took a tuft of Carex riparia, Scirpus lacustris, or Typha latifolia, but did not tear it off and just placed it on the water surface. They arranged a kind of “grass carpet” for the chick, so it did not have to swim. The chick didn’t lose energy to move across the plots overgrown with tall sedge when it followed the adults. When in danger, it “plunged” from the “nursery” into tall sedge and hided there. The hatching process lasted for 44 days (10 seasons on three permanent study plots), whereas “nurseries” were found there only during 16 days, in the period between 4 and 20 May. The median date of hatching was 11 May (120 out of 228 nests); the median date of registration of “nurseries” fell on 12 May, i.e., a day later. Over 9 seasons, 76 “nurseries” were found near 34 (100.0%) nests (22 pairs) on three permanent study plots. The number of “nurseries” within the nesting territory of a pair was different. Thirteen nests (38.3%) had only one “nursery” nearby; two “nurseries” were found near 8 nests (23.5%), three near 6 nests (17.6%), four near 5 nests (14.7%), and 2 nests (5.9%) had 5 “nurseries” each. Three pairs out of 22 had “nurseries” in three different seasons. The majority of “nurseries” (92.2%) were located close to the nests or no farther than 40 m away from them; only 7.8% of “nurseries” were constructed at a distance of 40 to 150 m from the nests. Peculiar traits of nest constructions of “true cranes” could be probably used in taxonomy. Their diversity within a small group (7 Palearctic species of 2 genera) is noteworthy. Demoiselle cranes place their nests on dry flat elevations, as close to the sources of drinking water (including those of anthropogenic origin) as possible. The lesser sandhill cranes construct nests on hillocky tundra with abundant water bodies of different types; they evidently do not use these water bodies as defensive barriers against predators, because of the polar day and a wide view of the terrain. Placement of the nests by Siberian cranes must be determined by the dominating landscape of the habitats, wide view of the vicinities, and the absence of predators rather than by the polar day. Finally, white-naped, red-crowned, common, and hooded cranes inhabiting regions lacking midnight sun (and for the latter two species tree vegetation often interferes with the wide view) construct nests exclusively in the shallow parts of different water bodies. In the darkness, it allows them to hear the approaching predator in advance. Thus, a certain species-specific dependence of cranes nest constructions on the type of substrate in the nesting habitats indicates high ecological flexibility of Gruidae that allowed the family to colonize almost the entire Palearctic. The data reported here might of importance for research on taxonomy of cranes as well.