Vassilis Goutner

Comparative Nest Site Selection and Breeding Success in 2 Sympatric Ardeids, Black-Crowned Night-Heron (Nycticorax nycticorax) and Little Egret (Egretta garzetta) in the Axios Delta, Macedonia, Greece

-We studied nest site selection and breeding success of Black-crowned Night-Herons (Nycticorax nycticorax) and Little Egrets (Egretta garzetta) in the Axios Delta (Greece) from 1988 to 1990. Both species nested above the middle of tamarisks and alders. Nest density varied each year from 333.3 nests/ha to 646.2 nests/ha for Blackcrowned Night-Herons and 291.7 nests/ha to 421.5 nests/ha for Little Egrets. Black-crowned Night-Herons started to breed earlier than Little Egrets, also placing their nests higher (mean nest height: 4.21 ? SD of 0.80 m and 3.54 ? SD of 0.71 m for Black-crowned Night-Herons and Little Egrets, respectively). The nearest neighbors were conspecifics for Black-crowned Night-Herons and heterospecifics (Black-crowned Night-Herons) for Little Egrets. The mean distance of the nearest neighbor was similar in both species (1.02 ? SD of 0.46 m and 1.11 ? SD of 0.37 m for Black-crowned Night-Herons and Little Egrets, respectively). In contrast to late-nesting Little Egrets that located their nests lower, Black-crowned Night-Herons maintained a constant nest distance from the ground. The mean clutch size (3.40 ? SD of 0.60 and 4.32 ? SD of 0.81 for Black-crowned Night-Herons and Little Egrets, respectively) and the mean chick survival per nest (2.48 ? SD of 0.95 and 2.53 ? SD of 1.28 for Black-crowned Night-Herons and Little Egrets, respectively) of both species varied among the study years. No variation was observed in the means of clutch size and chick survival per nest of Black-crowned Night-Herons among the 3 sub-periods of the breeding season. Little Egret clutch size and mean number of eggs hatched was smaller in late nesters, but no difference was observed in chick survival per nest between early and late nesters. Nest placement did not affect chick survival in Black-crowned Night-Herons and only marginally in Little Egrets. Received 5 March 1997, accepted 27 September 1997.

Mercury in feathers of Squacco Heron (Ardeola ralloides) chicks in relation to age, hatching order, growth, and sampling dates

We studied the relationships between mercury content of Squacco Heron (Ardeola ralloides) chick body-feathers and nestling age, hatching order (seniors-juniors) and growth parameters, and the date of feather sampling in the Axios Delta, northern Greece, in 1993 (n = 75 chicks) and 1994 (n = 80). Mercury levels were not significantly correlated with chick age in either year of the study. Most of the variability in mercury (90%) was found among broods, attributable to differential prey selection and/or foraging habitat and patch utilization by parents. Within broods, juniors had significantly higher mercury loads than seniors in 1993, but there was no significant difference between the two in 1994. Correlations of nestling weight and linear measurements corrected for chick age and mercury concentrations were never significant and explained small amounts of variability in chick growth. However, linear measurements corrected for age were significantly higher among seniors in 1993, when those nestlings had lower mercury loads than their siblings. Mercury levels were unaffected by the date of feather collection in 1993, but exhibited a significant increase over time in 1994. This can be attributed to a shift towards more highly contaminated habitats and prey types by foraging parents, resulting from seasonal changes in water level and vegetation cover in important foraging habitats. Feather collection from Squacco Heron nestlings late in the breeding season seems to be an appropriate method for biomonitoring mercury pollution in the Axios Delta.

Diet of the White Stork in Greece in Relation to Habitat

Abstract Prey taken by breeding White Storks (Ciconia ciconia) were studied using pellets collected from 1993 to 1995 within its breeding area in Greece. Prey consisted of orthopterans, coleopterans, other insects, mollusks and vertebrates. The difference in the proportions of these taxa was significant among major foraging habitats (lakes, rivers, deltas and dry habitats). With the exception of the rivers, major habitats tended to group together in clusters, suggesting that similar prey types were available to the storks in common habitat types.

Sex Determination of Great Cormorants (Phalacrocorax carbo sinensis) using Morphometric Measurements

Abstract Great Cormorant (Phalacrocorax carbo) is monomorphic in plumage such that sexes cannot be separated by plumage characteristics. In contrast, it displays sexual size dimorphism, with males generally being larger than females. Sexual dimorphism and variability in size of the continental Great Cormorant (P. c. sinensis) was studied in Greece to develop useful sexing techniques using morphometric measurements. Body mass, wing, culmen, and tarsus length of 81 birds controlled under license were measured during the wintering season in 1999-2002. The sex of each bird was determined by dissection and gonadal inspection. Forward stepwise discriminant analyses were performed to provide reliable functions that would enable the prediction of sex of a bird. Differences in size between adult and juvenile birds were not significant in both sexes, whereas males were larger than females in all measurements. Body mass (19.2%) and culmen length (11.1%) were the most dimorphic variables of those looked at followed by tarsus (6.5%) and wing (6.1%) length. Although wing length was the least dimorphic variable, it also displayed the lowest coefficient of variation (2.3%) thus being the best single measurement for separating the sexes. Three discriminant functions that correctly classified 92.6-95.1% of Great Cormorants of this sample were produced. These functions were reliable (similar accuracy for discriminant analysis and jackknife validation) and seasonally unbiased, as body mass was excluded from the analyses. The function including wing and culmen length as variables showed somewhat lower accuracy when tested with a new sample from The Netherlands suggesting that the obtained functions should be applied with caution to other populations, especially within the area of overlap between the sexes, unless inter-population sources of variation (e.g., geographic variation, hybridization, inter-observer bias) are sufficiently understood.

Sexual differences in the diet of great cormorants Phalacrocorax carbo sinensis wintering in Greece

Sexual differences in the diet of the great cormorant, Phalacrocorax carbo sinensis, were studied in four Greek wintering areas, the Amvrakikos Gulf, the Axios and Evros Deltas and the Messolonghi Lagoon, through the analysis of stomach contents. Great cormorants are birds sexually dimorphic in size, with males being generally larger than females. Although similar prey species were found in the stomachs of both sexes in all the studied areas, significant differences were observed with respect to the proportion of species taken. Male birds ate higher proportions of large fish species such as grey mullets, European sea bass, Dicentrarchus labrax, and Prussian carp, Carassius gibelio, while female birds took higher proportions of smaller species such as big-scale sand smelt, Atherina boyeri, and black goby, Gobius niger. As a consequence, male great cormorants were found to feed on significantly larger prey than did females by means of fish standard length and body mass. There was no significant difference between the sexes in the mass of food found in stomachs.

Spatial Patterns of Winter Diet of the Great Cormorant in Coastal Wetlands of Greece

Abstract Diet of the Great Cormorant (Phalacrocorax carbo) was studied in three coastal wintering areas (Axios and Evros Deltas, Messolonghi Lagoon) of Greece, in order to assess spatial differences and commercial value of prey. Thirteen birds were collected from the Axios Delta, 28 from the Evros Delta, and 16 from Messolonghi Lagoon. Pellets were collected from the Evros Delta (26) and Messolonghi Lagoon (30). A variety of fish taxa were found in the samples, but only one or two dominated in Great Cormorant’s diet, either by numbers or biomass. Grey mullets (Mugilidae and Golden Grey Mullet Liza aurata) were the most important prey by numbers and biomass in the Axios Delta; Giebel (Carassius auratus gibelio) dominated by numbers and biomass in the Evros Delta; whereas Boyer’s Sand Smelt (Atherina boyeri) was most important by numbers and Mugilidae by biomass at Messolonghi Lagoon. Differences found in diet between areas are probably due to differences in prey species composition and abundance. Fish of high commercial value contributed in low proportions in Great Cormorant’s diet, by numbers and biomass, being highest at Messolonghi Lagoon (22.4% by numbers, pellets; 11.5% by biomass, stomachs). The small overlap between the bird’s diet and valuable prey suggests minimal competition with fisheries.

Low mercury contamination in Mediterranean gull Larus melanocephalus chicks in Greece

Mercury (Hg), a toxic heavy metal harmful to animals, commonly occurs in Mediterranean ecosystems. Mediterranean gull Larus melanocephalus numbers have declined considerably in Greece since the 1990s. Mediterranean gull chicks’ back feathers were therefore collected from three Greek colonies in different years between 1999 and 2009 to assess Hg pollution in this larid. Hg concentrations varied with arithmetic means ranging between 815 ng g−1 dry weight (dw) (Lafri Lagoon in 2000) and 1264 ng g−1 dw (Evros Delta in 2000), and values were independent of chick age, although significant among-year and among-site variations were found. Hg concentrations in Greek Mediterranean gull chick feathers were generally low and in fact lower than those associated with adverse effects in other bird species. Comparisons with other studies revealed that Hg concentrations in Mediterranean gulls from Greece were mostly lower than those found in other gull species elsewhere in the world. This study presents the first data on Hg contamination in the Mediterranean gull. The results might be useful in understanding and evaluating the birds’ exposure to this highly toxic pollutant and its impact on both local populations and the wider ecosystem.

Organochlorine residues in blood of cinereous vultures and Eurasian griffon vultures in a northeastern Mediterranean area of nature conservation

In the National Park of Dadia-Lefkimi-Soufli Forest (Dadia NP, Greece), seven “target” PCBs and 16 organochlorine pesticides (OCs) were analysed in blood samples of cinereous vultures (Aegypius monachus) and Eurasian griffon vultures (Gyps fulvus). PCB congeners 138, 153 and 180 predominated in both species’ blood samples. In both species, no differences were detected in congener levels between successive age classes, but in cinereous vulture, there were significant differences between adult and nestling in levels of PCB 28, 52, 101, 118 and between nestling and immature in levels of PCB 101. Regarding pesticides, p,p′-DDE dominated in both vultures followed by β-HCH, lindane and endosulfan sulphate, but ∑OCs were higher in griffon vulture. Significant differences were detected only between nestling and sub-adult cinereous vultures in heptachlor levels and between nestling and adult in p,p′-DDT. The origin of pollutants differs between the two vulture species and pollution patterns may not reflect those at Dadia NP.

Factors Affecting the Foraging Behavior of the Squacco Heron

Abstract The foraging behavior of adult and recently fledged juvenile Squacco Herons (Ardeola ralloides) was studied during the breeding season at the Axios Delta, northern Greece. Adults were more efficient foragers than young birds and they had a 37% higher success per peck rate. The majority of adults captured some large prey items, while most juveniles caught only small prey. A comparison between the two age classes, as well as seasonal trends in adult data, indicated a negative association between prey size and foraging rates. Adult and juvenile foraging behavior did not vary significantly between morning and evening. Herons that moved faster also had higher pecking and capture rates, but a lower success ratio. Moving rate did not appear to be correlated with prey size. Herons moved at a slower rate along the edge of dense reed beds, probably in response to this habitat’s physical structure. Adults caught a greater proportion large prey items in open-water areas than in areas with more vegetation.

Lead and cadmium in eggs of colonially nesting waterbirds of different position in the food chain of Greek wetlands of international importance

Lead and cadmium concentrations were measured in eggs of collonially nesting waterbirds with different position in the food chains of Greek wetlands of international importance. Differences were found between species in the levels of both lead and cadmium in the Evros and Axios Deltas attributable to their different diets. Nevertheless, the concentration in eggs was unrelated to the position of each species studied in its food chain. There was no significant difference in lead levels among four wetlands sampled for the cormorant and in Cd levels among three wetlands sampled for the Mediterranean gull, probably implying species-specific accumulation patterns. A higher lead pollution of the Axios Delta area was only reflected in the eggs of the Mediterranean gull. The very low concentrations of both metals found in the eggs may either suggest low environmental inputs or lack of sensitivity in using eggs as lead and cadmium biomonitors, thus a more sensitive bioindicator still remains to be found.