Branta Issues

Ontogeny of the Demoiselle Cranes in South-Eastern Ukraine.

S. V. Winter ¹, P. I. Gorlov ², Y. A. Andryushchenko ³, S. N. Podorozhnyi ⁴, K. A. Postelnykh ⁵

In 1982-1989 in the Zaporozhye Region (study area in Makovka village, 47°01` N, 35°57` E), on Sivash (Churyuk Island, Novotroitskiy district, Kherson Region, 46°06` N, 34°11` E), and Kerch Peninsula of the Crimea, we studied ontogenetic development of the Demoiselle Crane, Anthropoides virgo, on the base of 21-23 chicks of 14 pairs. In addition to weighing, 15 external morphological characters were measured. The presence of ovipositor teeth, the condition of the subclavian tip, the yolk sac apteria, the apteria on the wing tip, the colour of non-feathered body parts, the size of wing claws on the fingers (on digitus. alularis, dig. major) were monitored. Changes in these parameters were traced from hatching to the beginning of flight (age 48 days).
The chicks hatch from 16.05 to 3.07, with a peak on 21-30.05, according to 8-season observations. The correlation (r = 0.91) between egg volume and weight of the hatched chick was revealed: y = 4.7417 + 0.6383 х, where x is the volume of egg, cm³.
In a barely hatched «wet» chick, the yolk sac (measured crosswise, 21 x 18 mm) was oriented (as in the Common Crane chick) across the body axis, but in 2-3 hours it had a rounded shape (from 10 x 9 to 12 x 9 mm) and oriented with its long axis along the body, reducing the area by 3.45 times.
In 2 nests, chicks were examined every 6 hours; in one nest, where chick weight was monitored until 40 hours, weight continued to decrease; in the other nest, between 25 and 50 hours, weight already increased.
Embryonic plumage was described for 5 chicks at the age of 1-3 days from 3 nests. It is known that the pattern of embryonic plumage of cranes is a topographic scheme of their pterilias and apterias (Kashentseva, Tsvetkova, 1995; Ilyashenko, 2006). However, this «axiom» has a weak point: non-contrast and relatively monotonous coloration of the embryonic plumage of Siberian Crane (Grus leucogeranus) and Hooded Crane (G. monacha) is very difficult to «tie» to pterilography. The pattern of differently coloured sections of the embryonic down does not necessarily «copy» the boundaries of pterilias and apterias. 
The description of the embryonic plumage of the cranes should be founded not only on the position of pterilias and apterias, but also on the colour of its different parts. In this situation detailed photographies of downy chicks in good light can help (see Kashentseva, 2020)
In the embryonic plumage of the Demoiselle Crane there are two, existing for about 7-14 days, temporary apteria that have not yet been noticed so far. 
The first is associated with the areas surrounding the yolk sac (called by us the yolk apteria, Apterium vitellinum; Winter, Gorlov, 2019; 2021). Initially convex and protruding above the abdominal surface, the yolk sac loses volume and area as its contents are depleted, and its areas devoid of embryonic down, after 7-10 days of life, are overgrown with a new generation of down. At this point the apteria ceases to exist.
Another temporary apteria of the embryonic plumage of the Demoiselle Crane is located on the upper surface of the wing tips, with black-grey naked skin. Its size and shape differ significantly from the carpal apteria described for the adult Chicken (Gallus domesticus), Great Horned Owl (Bubo virginianus) and Common Crane (Grus grus), in which it has the form of a narrow strip (Lukas, 1972; Lukas, from Baumel, 1979; Kashentseva, 1988), but does not occupy almost all dorsal surface of the wing tip. The dissimilarity of its outline and shape in downy chicks and adult cranes compels the suggestion of the term embryonic dorsal (upper) carpal apteria (Apteria manuale embrionale). It can probably also be present in precocial chicks of other groups of birds (Winter, Gorlov, 2019). By 10-12 days of age, the area of this apteria had significantly increased and the skin on it had darkened, and by the 20th day the apteria was completely overgrown, probably with mesoptile down (mesoptile plumae) of types I and II (Firsova, 1975; Ilyashenko, 2006).
Interestingly, we observed a similar embryonic carpal apteria before and in the barely dried chick of the Moorhen Gallinula chloropus (N. Azov Region, Ukraine), and later in the downy chicks of the Coot (Fulica atra), on artificial ponds in Frankfurt am Main and Berlin, Germany. 
From day 5-7 and up to day 40-41, a brown or dark grey transverse stripe appears on the beak between distal border of nostrils and last ¼ (proximal border of ovipositor teeth sole), with indistinct boundaries. Later than 45 days of age, it disappears. A very similar, but more contrasting transverse stripe is present on the beaks of Common Crane and Sandhill Crane (Grus canadensis) chicks, less contrasting in Red-crowned Crane (Grus japonensis) and Hooded Cranes (Winter, 1977; Winter et al., 2015; Winter, Gorlov, 2019; 2021), but it is not known in the downy chicks of White-naped Crane (Grus vipio; Smirenskiy, Iliashenko, 2006).
Interestingly, a more contrasting darker transverse stripe is present here and on the beaks of week-old Coot and Moorhen chicks, but is absent in chicks of Corncrake (Crex crex), Spotted Crake (Porzana porzana) and Water Rail (Rallus aquaticus; Salzer, 1996). 
The length and colouration of the rudimentary claws on the phalanges of the 1st and 2nd wingtips were monitored until 26 days of age (10.4-fold increase in body weight!). They may have grown a little later (as in the Sandhill Crane; Winter, Gorlov, 2020), but up to this age they were almost unchanged.
A comparison of the size of young and adults in the last week before flight (39-49 days) showed that young (n = 10) had the least developed beak to nostril (52.2% of the adult mean; n = 11), while metatarsal length had already reached the adult mean. Not surprisingly, with the tail reaching 62% and the wing at 69% of that of adults, from a distance young birds appeared to be taller than adults. At the same time, in July and the end of the second decade of August their average body weight was 1.629 ± 0.097 kg (n = 10), and 3 young females in October (age 6 months) from the Oka State Nature Reserve breeding centre weighed by 1.0 kg more. Previously, we pointed out that in the International Crane Foundation's breeding centre (Wisconsin, USA), young birds weighed significantly more before flight than in the wild in Ukraine (Winter et al., 1999). T.A. Kashentseva (2020) gives a mass of 1850 g for a 36-41 day-old female, 1900 g for a 41-50 day-old female, and even 2050 g for a 51-55 day-old female, while the chicks we measured weighed less than 1971.3 g before flight.
When the observer approached, 5 chicks at 43-46 days old failed to take off, and the first flight of the young was recorded at 46 days of age. Late fledglings, 47-49 days old, flew 200-1500 m and 52 days old were flying confidently. Thus, the mean age (lim = 46-52) of newly fledged young was 48.0 ± 0.6 days (n=9; Cv = 3.76%; Nik.N. and Nat.N. Andrusenko, 1987; our data). Wing length of newly fledged young was 345.0-366.0 mm, tail length was 107.3-115.0 mm, and body weight was 1419.8-1971.3 g.
Still Berezovikov (1981) observed that in the last three decades of the 20th century, the Demoiselle Crane started breeding in cultivated fields, bare or with low and sparse herbaceous vegetation, but with soil of a different microstructure than in natural habitats. This difference plays an important role because after rains the wet soil adheres to the feet of the breeding birds and then covers the surface of their incubating eggs so that they «turn into two lumps of soil”. This peculiarity of eggs of «agrocenotic» Demoiselle Cranes is not known for representatives of the genus Grus.
The thesis on the higher staining of Demoiselle Crane eggs on agrocenoses is wonderfully proved by comparison of three sites of the Demoiselle Crane breeding range. In the Zaporozhye Region and on the Kerch Peninsula of the Crimea, all or most of the nests are located in the agrocenoses, but on the Tarkhankut Peninsula, because of abundant limestone soils and outcrops of limestone on the daytime surface, the frequency of dirty eggs in the Demoiselle Crane clutches was significantly lower. Undoubtedly, 'masking' of clutches by mud increases their probability of going undetected (wild boar, Sus scrofa; fox, Vulpes vulpes; feral dog, Canis familiaris; rooks, Corvus frugilegus; Hooded Crows, C. corone and Ravens, C. corax), but possibly the mud adhered to the egg disrupts oxygen exchange by closing pores in the shell and worsening conditions of embryo breathing.
An influence of the rainfalls on the chicks in the first decade of their life had a negative effect. At first the thick mud adhered to their beaks and toes, then it quickly hardened, to a 'stony state', and therefore prevented them from eating and moving about. When trying to free the beaks and toes of the chicks from it, the surface layer of epidermis was removed from the fingers and beaks along with the hardened mud.