Author/Editor		Janžekovič, Franc; Štumberger, Borut; Denac, Damijan
Title		Velikost legla, velikost jajc in fenologija prihoda na gnezdišče pri navadni čigri Sterna hirundo v SV Sloveniji
Translated title		Common tern's Sterna hirundo clutch size, egg dimensions and phenology of its arrival to the breeding site in NE Slovenia
Type		članek
Source		Acrocephalus
Vol. and No.		Letnik 24, št. 117
Publication year		2003
Volume		str. 61-6
Language		slo
Abstract		Common Terns Sterna biruraclo began to return to their breeding sites on the Drava river in early April. The article presents the measurement of 471 Common Terns' eggs from 184 nests. Average clutch size was 2.55 (median = 3, min = 1, max = 4) eggs per nest, with an average egg size of 41.1 x 30.3 mm. There was no characteristic difference in the average egg length between the two-, three- and four-egg clutches. Concerning the average breadth of eggs, characteristic differences were noted particularly in four-egg clutches. Correlation between egg length and breadth was very loose (r = 0.25, p < 0.0001). Egg length was more variable (CV%EL = 4.33) than egg breadrh (CV%EB = 2.96). Size patterns in Common Terns clutches were not quite consistent with the brood-reduction hypothesis, according to which every egg laid in a single nest is smaller than the previous one.
Summary		Navadne čigre Sterna hirundo so se v gnezdilni okoliš na območju Drave vračale v začetku aprila. V članku predstavljamo meritve 471 jajc iz 184 gnezd navadne čigre. Povprečna velikost legla je bila 2,55 (mediana = 3, min = 1, max = 4) jajc na gnezdo, povprečna velikost jajc je bila 41,1 x 30,3 mm. Med dvo-, tro- in {tirijajčnimi legli ni bilo značilne razlike v povprečni dolžini jajc, v povprečni širini jajc pa so se značilno razlikovala predvsem legla s {tirimi jajci. Korelacija med dolžino in širino jajc je bila zelo ohlapna (r = 0,25, p < 0,0001). Dolžina jajc je bila variabilnej{a spremenljivka (CV%EL = 4,33) od širine (CV%EB = 2,96). Velikostni vzorci jajc v leglih navadnih čiger se ravno ne ujemajo s hipotezo manj{anja legla (brood-reduction hypothesis), po kateri je vsako izleženo jajce znotraj enega gnezda manjše od predhodnega.
Descriptors		BIRDS NESTING BEHAVIOR BEHAVIOR, ANIMAL ECOSYSTEM