The breeding biology of the black‐crowned night‐heron (Nycticorax nycticorax) and the little egret (Egretta garzetta) at the Huleh Nature Reserve, Israel

Abstract

With 2 figures in the text)The breeding biologies of the black-crowned night-heron (Nycticorw; nycticorax) and the little egret (Egrertu garzettu) were studied in the mixed heron breeding colony at the Huleh Nature Reserve, Israel, from 1977. Both studied species have resident (30%) and migrating populations. The colony consisted of about 3,000 pairs of seven breeding species nesting in 5-7 highly synchronous mixed species sub-colonies from mid-March to mid-September. Mean time-lapse between initiation of two sub-colonies is 20.45 days. Mean duration of egg-laying within a sub-colony is 12.45 days and of hatching is 12.38 days. Nests are built each year mainly with papyrus stems and there are significant differences among little egrets, night-herons and cattle egrets in their tendency to use different nesting material. Mean clutch size was 3.41 for little egrets and 2.97 for night-herons, while the most frequent clutch size was three in both species (54.9% and 68.5%, respectively). Mean fresh laid egg masses were 27.1Sg and 31.33g for little egrets and night-herons, respectively. The variability in egg mass within a clutch was significantly smaller (on average 12 times and 7 times for little egrets and nightherons, respectively) than between clutches. Incubation of each egg lasts 21.6 days in little egrets and 21.1 days in night-herons. Mean egg mass loss during incubation was 14.6% and 13.8% for little egrets and night-herons, respectively. Hatching success is 90.2% (n = 177) in little egrets and 92.4% (n = 258) in night-herons, and hatching order is related to laying order in both species. Hatchling's mass at hatch ranged from 13-26 g (n = 34), 74.8% of initial egg mass for little egrets and 19-29 g (n = 30). 73.8% of initial egg mass for night-herons. Chick development rates were studied in nature and in captivity. In both species there is a linear correlation between a chick's age and its body dimensions. Chicks reach adult dimensions at about one month and fledge at the age of 35-42 days. Fledged chicks disperse during the first year up to 50-6Okm from the colony. Survival rates for chicks up to the age of 28 days are 69.9% and 56.6% for little egrets and night-herons, respectively. The main mortality factor for eggs and chicks is probably predation by avian predators. Data on minimum longevity, 10-1 I years for little egrets and 7-8 years for night-herons, were obtained from resightings of tag-marked individuals. Long-term monitoring and study of the structure and breeding parameters of a regionally important colony in relation to known environmental effects are an essential tool for conservation and management plans for colonial species.

Low breeding success of the little egret (Egretta garzetta) near residential areas and in colonies exposed to gales: a comparison of colony in Sichuan, Southwest China, with literature

“…1997; Parejo et al. 2001), as well as in Asia (Ashkenazi and Yom-Tov 1997) and especially in central and southern China (Shi et al. 1991; Yang 2000; Zhang et al.…”

Three-dimensional niche partitioning between two colonially nesting ardeid species in central China

“…There have been numerous studies on niche partitioning between ardeid species, but most of them have only investigated the diets of various herons (e.g., Trexler et al 1994;Salazar et al 2005;Boyle et al 2012;Choi et al 2016;Ashoori et al 2017). And there were a few studies on nest site selection (Jenni 1969;McCrimmon 1978;Burger 1979;Parejo et al 1999;Metallaoui et al 2020) and temporal separation between species within heron colonies (Weber 1975;Burger 1978;Ashkenazi and Yom-Tov 1997). Despite those separate studies of diet, nest site selection and nesting phenology, we still do not have a comprehensive understanding of niche partitioning that integrates the temporal, spatial and trophic dimensions of sympatric ardeid species.…”

Οικολογία και προστασία του νυχτοκόρακα, Nycticorax nicticorax nycticorax L.,1758, στην τεχνητή λίμνη Κερκίνη του Ν.Σερρών

“…8:00-10:00 10:00-12:00 12:00-14:00 14:00-16:00 16:00-18:00 18:00-20:00 (Kushlan 1978, Forbes 1989, Ashkenazi and Yom-Tov 1997, Kazatzìdis 1998, β) τα άτομα των ειδών που φωλιάζουν στην αποικία ανταλλάσσουν πληροφορίες σχετικά με την ύπαρξη και τη θέση θέσεων τροφοληψίας (Krebs 1974, Burger 1981, Bayer 1982b, Forbes 1989, γ) αξιοποιούν αποτελεσματικότερα τους διαθέσιμους πόρους με το να φωλιάζουν κοντά σ' αυτούς (Kushìan 1978) και δ) ο συγχρονισμός της έναρξης της αναπαραγωγικής διαδικασίας των περισσοτέρων ζευγαριών οδηγεί, έμμεσα, στον περιορισμό της αρπακτικότητας λόγω της παραγωγής τροφής (αβγά και νεοσσοί) για μικρό χρονικό διάστημα (Burger 1981).…”

“…Ωστόσο οι διαθέσιμες θέσεις για φωλεοποίηση περιορίζονται έτος με το έτος γιατί το παραλίμνιο δάσος συρρικνώνεται μετά το 1982 (Crivelli et al 1995 (Burger 1981). Επιπρόσθετα δεν υπάρχουν αβγά και νεοσσοί στο διάστημα μεταξύ ιης εγκατάστασης των υποαποικιών αναγκάζοντας έτσι τα αρπακτικά να στραφούν σε άλλες πηγές τροφής (Ashkenazi and Yom-Tov 1997). Οι ίδιοι ερευνητές διαπίστωσαν ότι ο καλαμόκιρκος και η σταχτοκουρούνα δραστηριοποιούνται σε νεοεγκατεστημένες υποαποικίες, Η σταχτοκουρούνα, η καρακάξα και ο καλσμόκιρκος ήταν οι "κύριοι άρπαγες που παρατηρήθηκαν στις αποικίες της λίμνη Κερκίνης.…”

“…Οι νεοσσοί διαφορετικών ηλικιών έχουν διαφορετικές φωνές σε κάθε υποαποικία βοηθώντας τα αρπακτικά να αναγνωρίζουν το στάδιο ηλικίας τους (Ashkenazi and Yom-Tov 1997 (Burger 1981).…”