Environmental Monitoring and Assessment, Mar 31, 2022
Environmental pollution and climate change are causing major changes in the marine environment. C... more Environmental pollution and climate change are causing major changes in the marine environment. Coastal zones around the world are experiencing changes such as nutrient influx, resulting in altered plankton communities. The aim of this study was to determine the response of zooplankton to the changes in the environmental variables in the coastal zone of the Arabian Sea, Southwest Coast of India, over 10 years. Zooplankton abundance, chlorophyll-a concentrations, and water quality variables (rainfall, nitrates, phosphates, pH, water temperature, and salinity) were quantified from January 2010 to December 2019. Water temperature, pH, salinity, and phosphates increased steadily across the sites during the study period whereas chlorophyll-a and nitrates decreased. Rainfall abundance was not exhibiting any patterns or trends. The effects of the sampled environmental variables on zooplankton abundance were tested using generalized linear mixed models. Salinity and phosphates negatively affected the zooplankton abundance whereas water temperature, pH, and chlorophyll-a concentration had a positive effect. Coastal zones in southwest India are experiencing declining phytoplankton abundance due to a number of environmental factors. Reduced phytoplankton combined with altered environmental variables are having declining effects on zooplankton. This decline in zooplankton population has far reaching effects on biota in higher trophic levels including economically important organisms such as fishes.
Background The Maghreb Magpie (Pica mauritanica) is an endemic North African species. Available k... more Background The Maghreb Magpie (Pica mauritanica) is an endemic North African species. Available knowledge on this species is limited to historic descriptive data with no ecological information provided. Populations continue to dramatically decline in Tunisia, where only one relic population survives. Investigating the breeding biology of this species is essential for conservation purposes. The purpose of this study was to increase our understanding of the Tunisian relic population and provide detailed data on breeding biology over two breeding seasons (2017 and 2018). Methods This study occurred on a private farm of 650 ha, located 10 km from Dhorbania village at Kairouan Governorate, in central Tunisia. Active nests were monitored weekly during egg laying period and twice a week during hatching period. The Ivlev’s electivity index was used to assess whether the frequency of use of nesting trees and bushes matched their availability in the study area. We recorded nest measurements a...
Au cours de la période du début mai à début août (2014), un suivi de la reproduction du Flamant r... more Au cours de la période du début mai à début août (2014), un suivi de la reproduction du Flamant rose Phoenicopterus ruber au Cap Bon (Tunisie) a été réalisé en surveillant la première tentative de nidification de cette espèce dans la région, et ceci au sein d'une héronnière récemment installée. Nous avons déterminé la taille et la composition du peuplement nicheur, examiné la chronologie d'installation des différentes populations et mesuré le succès reproducteur de chaque espèce. La colonie a hébergé 3 grands échassiers : le Flamant rose, l'Aigrette garzette Egretta garzetta et le Héron garde-boeufs Bubulcus ibis. En tout, 580 flamants (adultes et immatures) ont été recensés. La population nicheuse des flamants a atteint 97 couples (69.3% des adultes). La colonie est dominée par les garde-boeufs (67.2%) suivis par les flamants (23.8%) et les aigrettes (8.8%). L'Aigrette gazette s'étant installée la première semaine de mai (avec un pic du 05 au 15 mai). Elle a été...
Tunisian geckos count nine species (1 is insular relict, 1 is endemic, 2 are ubiquitous and 5 are... more Tunisian geckos count nine species (1 is insular relict, 1 is endemic, 2 are ubiquitous and 5 are enfeoffed). We aim to determine factors influencing their distributions. Surveys were founded on environmental divisions. Presence/absence data for 113 grids were analyzed using multivariate tools. 18 environmental variables were revealed and clustered into five factors to model species distributions. Established models were further projected on non-explored areas within Tunisian territory. The distribution of continental geckos follows an indirect bidirectional gradient; the South-northward one is physiologically stressful and the North-southward one is biologically stressful. Five biogeographic regions were established showing concordance with climatic and vegetation regionalization. The distribution of non-anthropophilic species is positively correlated to thermal amplitudes gradient. The distribution of anthropophilic taxa is positively correlated to agricultural land-use. Oasis, se...
We studied reproduction patterns and habitat use by Herons at Lebna, Chikli and Ichkeul wetlands ... more We studied reproduction patterns and habitat use by Herons at Lebna, Chikli and Ichkeul wetlands in Northern Tunisia during 2009 and 2010. The largest number of herons was recorded at Ichkeul after completion of breeding. Cattle Egrets preferred farmlands but also inhabited marshes. However, all other species (Grey Herons, Great White Herons, Little Egrets and Squacco Herons) seemed to be much dependent on marshes and rivers. The distribution of heron species among habitats varied significantly with years and seasons. Variations of reproductive parameters were revealed between sites, biotopes and years. The most successful nesting points were recorded at Ichkeul for both Little and Cattle Egrets. At Chikli breeding parameters were catastrophic. Losses concerned mainly nests built on the ground; those arboreal had a significantly higher reproductive performance. The clutch size of Cattle Egrets varied positively with diameter of nest at Lebna. Also, at Chikli, the height of nest had ...
This study was carried out at Galite archipelago over two consecutive breeding seasons (2014 and ... more This study was carried out at Galite archipelago over two consecutive breeding seasons (2014 and 2015). We investigated the breeding ecology of Eleonora’s falcon population in Galite archipelago by providing detailed data on its breeding biology and assessing the nesting parameters. Overall, 127 Eleonora’s falcon breeding pairs were recorded in all six islets of the archipelago. The eastern part of the archipelago hosted the highest number of breeding pairs with the highest density recorded at Gallo island (5.93 pairs/ha). Eleonora’s falcon breeding pairs mainly used the protected crevices non-exposed to sun and wind. The overall mean clutch size (mean ± SE) was 1.78 ± 0.10 eggs per clutch. Clutches of two eggs and one egg were the most frequent at Gallo and Fauchelle, respectively. The average hatched eggs per clutch and fledglings per brood were 1.29 ± 0.10 and 1.24 ± 0.10, respectively. The brood size varied significantly with clutch size and nest exposition being higher related ...
Abstract Shorebirds around the world have been undergoing significant declines as well as alterat... more Abstract Shorebirds around the world have been undergoing significant declines as well as alterations in patterns of migratory phenology due to major changes in the environment. Many of these changes have been linked with anthropogenic factors such as urbanization, environmental degradation, habitat loss and global climate change. We studied the abundance of 15 migratory shorebird species in a coastal wetland in western India that serves as an important stopover and wintering area by many shorebirds in the Central Asian Flyway. The study site was visited once a week during low tide (from 06:00–12:00 h) for 15 years (2005–2019). Shorebird abundance data was collected following direct count and block count methods. To study the departure of shorebirds we monitored shorebird numbers daily and collected benthic organisms three times a month from the shoreline habitats during low tide. Samples were collected from depths of 15 cm using a metal cylinder from areas that typically had the highest densities of foraging shorebirds. Daily rainfall, relative humidity, temperature of air and water and salinity were measured once a week. Generalized Linear Models GLMs (Gaussian family) was used to determine the variation in shorebird abundance in relation to environmental variables (relative humidity, water salinity, rainfall, water temperature, air temperature), and invertebrate prey abundance. We ran two GLMs with Poisson distribution of error to investigate if departure date varied with environmental variables and the abundance of invertebrate prey. Of the environmental variables, mean air temperature, water temperature and salinity increased significantly during the 15 years while invertebrate prey underwent steep declines. Ten of the 15 species’ declines were predicted by the changes in relative humidity, rainfall, water temperature, air temperature, salinity and invertebrate prey abundance. Departure dates also advanced in several species and were affected by relative humidity, air temperature, water temperature, salinity and invertebrate prey abundance. Our models suggest that salinity and invertebrate prey abundance were driving overall changes in shorebird abundance and departure dates. These two variables were negatively related (invertebrate prey abundance declined with increasing salinity). This was evident throughout the study period, during which salinity increased while invertebrate prey abundance declined. Species declines could be due to poor habitat quality and food availability resulting from environmental degradation. Delays in migration could be linked with inability to find enough high quality food to build up food reserves prior to departure. Better habitat management in key wintering wetlands and stopover sites along the flyway are needed help to restore populations of shorebirds.
ABSTRACT The Indian subcontinent is the primary wintering ground and stopover site for migratory ... more ABSTRACT The Indian subcontinent is the primary wintering ground and stopover site for migratory shorebirds to refuel along the Central Asian and South Asian Flyways. Despite the conservation importance of this region for migratory shorebirds, we lack information on the distribution and abundance of over-summering shorebirds—migrants that remain on their wintering grounds during the breeding season—to evaluate the impacts of anthropogenic change on this poorly understood life history strategy. We conducted weekly surveys of over-summering shorebirds at mudflats, mangroves, and sand beaches at the Kadalundi-Vallikkunnu Community Reserve on the southwest coast of India, 2005–2018. We examined long-term patterns of over-summering shorebird abundance, species composition, and habitat use and estimated proportional changes in over-summering abundance of each shorebird species documented at this globally important site. Over the 14 yr study, we documented 7 over-summering species, including Lesser Sand Plover (Charadrius mongolus), Whimbrel (Numenius phaeopus), Greater Sand Plover (Charadrius leschenaultia), Kentish Plover (Charadrius alexandrinus), Common Sandpiper (Actitis hypoleucos), Ruddy Turnstone (Arenaria interpres), and Pacific Golden-Plover (Pluvialis fulva). Mean abundance and species richness were higher at mudflats than at mangroves and sand beaches, with fewer individuals and species observed over-summering after 2010. Mudflats also had the highest species diversity and evenness compared to mangroves and sand beaches. Management plans that aim to restore vulnerable mudflats and mangroves and to reduce anthropogenic threats such as sand mining and waste dumping are needed to prevent the loss of important over-summering, foraging habitat for migratory shorebirds in southern India and along the Central Asian and South Asian Flyways.
The first case of breeding of the Glossy ibis Plegadis falcinellus in Tunisia has put the seal on... more The first case of breeding of the Glossy ibis Plegadis falcinellus in Tunisia has put the seal on several years of regular observations of wintering individual birds in pre and postnuptial periods, in several wetland areas of the country. Few individuals stay during the summer and 20 couples, recently settled at the fresh water reservoir at the Lebna dam near Cap Bon, nested in 2008. This first case of reproduction permitted the description and evaluation of some reproduction parameters observed at the nest site; average fertility, number of eggs per clutch, hatching and mortality rate.
Nine Ardeidae species breed in Tunisia. About 2,500-3,000 breeding pairs breed each year and more... more Nine Ardeidae species breed in Tunisia. About 2,500-3,000 breeding pairs breed each year and more than 12,000 individuals winter. The breeding population includes 8 regular species: Grey Heron Ardea cinerea, Purple Heron Ardea purpurea, Black-crowned Night Heron Nycticorax nycticorax, Cattle Egret Bubulcus ibis, Squacco Heron Ardeola ralloides, Little Egret Egretta garzetta, Little Bittern Ixobrychus minutus and Eurasian Bittern Botaurus stellaris (for the latter species, breeding is certain but no nest has been found). The Western Reef Egret Egretta gularis is a casual breeder. The Great Egret Casmerodius albus is present all the year round but no nesting has been found.
ABSTRACT Scopoli’s Shearwater (Calonectris diomedea) is a Procellariiform endemic to the Mediterr... more ABSTRACT Scopoli’s Shearwater (Calonectris diomedea) is a Procellariiform endemic to the Mediterranean Basin which is considered to be vulnerable in Europe due to recent local declines and its susceptibility to both marine and terrestrial threats. In the 1970s–1980s, its population size was estimated at 57,000–76,000 breeding pairs throughout the Mediterranean Basin, with the largest colony, estimated at 15,000–25,000 pairs, found on Zembra Island, Tunisia. The objectives of our study were to re-estimate the size of the breeding population on Zembra Island, to reassess the global population size of the species, and to analyse the implications of these findings on status and conservation of this species in the Mediterranean. Using distance sampling, we estimated the Zembra breeding population to be 141,780 pairs (95 % confidence interval 113,720–176,750 pairs). A review of the most recent data on populations of this species throughout the Mediterranean Basin led us to estimate its new global population size at 141,000–223,000 breeding pairs. Using the demographic invariant and potential biological removal approaches, we estimated the maximum number of adults which could be killed annually by all non-natural causes without causing a population decline to be 8800 (range 7700–9700) individuals, of which could be 3700 breeders. Although these results are less alarming in the context of species conservation than previously thought, uncertainties associated with global population size, trends and major threats still raise questions on the future of this species. More generally, we show how a monitoring strategy for a bird supposed to be relatively well known overall can be potentially misleading due to biases in survey design. The reduction of such biases would therefore appear to be an unavoidable prerequisite in cryptic species monitoring before any reliable inference on the conservation status of the species can be drawn.
Abstract We studied the reproduction patterns of Squacco Herons, Ardeola ralloides, during 2009–2... more Abstract We studied the reproduction patterns of Squacco Herons, Ardeola ralloides, during 2009–2010. This study was carried out in two colonies located at Ichkeul National Park (37.184992 N, 9.633758 E) and Lebna Dam (36.744161 N, 10.916569 E), in northern Tunisia. We determined the reproductive performance of the species, and investigated the relationship between reproductive parameters and nest characteristics (height and diameter). We registered successful nesting, with mean clutch size of 4.51 ± 0.85 for both years combined. Hatching success was 3.67 ± 1.07 eggs hatched/nest and fledging success reached 3.06 ± 1.28 young/nest. All reproductive parameters varied between years. The diameter and the height of nest had no effect on the clutch size, the initial brood size, or the final brood size at each site. We estimated the body condition index (BCI) and the growth curves of developing nestlings from repeated measurements of body mass, tarsus, head and bill length. The last chicks (rank four) to hatch had lower (BCI) and growth rates than the first, the second, and the third hatched chicks. These results stress the need for further protection measures be undertaken at Lebna Dam. Accessibility to the site should be highly controlled by the managers of Tunisian wetlands.
Environmental Monitoring and Assessment, Mar 31, 2022
Environmental pollution and climate change are causing major changes in the marine environment. C... more Environmental pollution and climate change are causing major changes in the marine environment. Coastal zones around the world are experiencing changes such as nutrient influx, resulting in altered plankton communities. The aim of this study was to determine the response of zooplankton to the changes in the environmental variables in the coastal zone of the Arabian Sea, Southwest Coast of India, over 10 years. Zooplankton abundance, chlorophyll-a concentrations, and water quality variables (rainfall, nitrates, phosphates, pH, water temperature, and salinity) were quantified from January 2010 to December 2019. Water temperature, pH, salinity, and phosphates increased steadily across the sites during the study period whereas chlorophyll-a and nitrates decreased. Rainfall abundance was not exhibiting any patterns or trends. The effects of the sampled environmental variables on zooplankton abundance were tested using generalized linear mixed models. Salinity and phosphates negatively affected the zooplankton abundance whereas water temperature, pH, and chlorophyll-a concentration had a positive effect. Coastal zones in southwest India are experiencing declining phytoplankton abundance due to a number of environmental factors. Reduced phytoplankton combined with altered environmental variables are having declining effects on zooplankton. This decline in zooplankton population has far reaching effects on biota in higher trophic levels including economically important organisms such as fishes.
Background The Maghreb Magpie (Pica mauritanica) is an endemic North African species. Available k... more Background The Maghreb Magpie (Pica mauritanica) is an endemic North African species. Available knowledge on this species is limited to historic descriptive data with no ecological information provided. Populations continue to dramatically decline in Tunisia, where only one relic population survives. Investigating the breeding biology of this species is essential for conservation purposes. The purpose of this study was to increase our understanding of the Tunisian relic population and provide detailed data on breeding biology over two breeding seasons (2017 and 2018). Methods This study occurred on a private farm of 650 ha, located 10 km from Dhorbania village at Kairouan Governorate, in central Tunisia. Active nests were monitored weekly during egg laying period and twice a week during hatching period. The Ivlev’s electivity index was used to assess whether the frequency of use of nesting trees and bushes matched their availability in the study area. We recorded nest measurements a...
Au cours de la période du début mai à début août (2014), un suivi de la reproduction du Flamant r... more Au cours de la période du début mai à début août (2014), un suivi de la reproduction du Flamant rose Phoenicopterus ruber au Cap Bon (Tunisie) a été réalisé en surveillant la première tentative de nidification de cette espèce dans la région, et ceci au sein d'une héronnière récemment installée. Nous avons déterminé la taille et la composition du peuplement nicheur, examiné la chronologie d'installation des différentes populations et mesuré le succès reproducteur de chaque espèce. La colonie a hébergé 3 grands échassiers : le Flamant rose, l'Aigrette garzette Egretta garzetta et le Héron garde-boeufs Bubulcus ibis. En tout, 580 flamants (adultes et immatures) ont été recensés. La population nicheuse des flamants a atteint 97 couples (69.3% des adultes). La colonie est dominée par les garde-boeufs (67.2%) suivis par les flamants (23.8%) et les aigrettes (8.8%). L'Aigrette gazette s'étant installée la première semaine de mai (avec un pic du 05 au 15 mai). Elle a été...
Tunisian geckos count nine species (1 is insular relict, 1 is endemic, 2 are ubiquitous and 5 are... more Tunisian geckos count nine species (1 is insular relict, 1 is endemic, 2 are ubiquitous and 5 are enfeoffed). We aim to determine factors influencing their distributions. Surveys were founded on environmental divisions. Presence/absence data for 113 grids were analyzed using multivariate tools. 18 environmental variables were revealed and clustered into five factors to model species distributions. Established models were further projected on non-explored areas within Tunisian territory. The distribution of continental geckos follows an indirect bidirectional gradient; the South-northward one is physiologically stressful and the North-southward one is biologically stressful. Five biogeographic regions were established showing concordance with climatic and vegetation regionalization. The distribution of non-anthropophilic species is positively correlated to thermal amplitudes gradient. The distribution of anthropophilic taxa is positively correlated to agricultural land-use. Oasis, se...
We studied reproduction patterns and habitat use by Herons at Lebna, Chikli and Ichkeul wetlands ... more We studied reproduction patterns and habitat use by Herons at Lebna, Chikli and Ichkeul wetlands in Northern Tunisia during 2009 and 2010. The largest number of herons was recorded at Ichkeul after completion of breeding. Cattle Egrets preferred farmlands but also inhabited marshes. However, all other species (Grey Herons, Great White Herons, Little Egrets and Squacco Herons) seemed to be much dependent on marshes and rivers. The distribution of heron species among habitats varied significantly with years and seasons. Variations of reproductive parameters were revealed between sites, biotopes and years. The most successful nesting points were recorded at Ichkeul for both Little and Cattle Egrets. At Chikli breeding parameters were catastrophic. Losses concerned mainly nests built on the ground; those arboreal had a significantly higher reproductive performance. The clutch size of Cattle Egrets varied positively with diameter of nest at Lebna. Also, at Chikli, the height of nest had ...
This study was carried out at Galite archipelago over two consecutive breeding seasons (2014 and ... more This study was carried out at Galite archipelago over two consecutive breeding seasons (2014 and 2015). We investigated the breeding ecology of Eleonora’s falcon population in Galite archipelago by providing detailed data on its breeding biology and assessing the nesting parameters. Overall, 127 Eleonora’s falcon breeding pairs were recorded in all six islets of the archipelago. The eastern part of the archipelago hosted the highest number of breeding pairs with the highest density recorded at Gallo island (5.93 pairs/ha). Eleonora’s falcon breeding pairs mainly used the protected crevices non-exposed to sun and wind. The overall mean clutch size (mean ± SE) was 1.78 ± 0.10 eggs per clutch. Clutches of two eggs and one egg were the most frequent at Gallo and Fauchelle, respectively. The average hatched eggs per clutch and fledglings per brood were 1.29 ± 0.10 and 1.24 ± 0.10, respectively. The brood size varied significantly with clutch size and nest exposition being higher related ...
Abstract Shorebirds around the world have been undergoing significant declines as well as alterat... more Abstract Shorebirds around the world have been undergoing significant declines as well as alterations in patterns of migratory phenology due to major changes in the environment. Many of these changes have been linked with anthropogenic factors such as urbanization, environmental degradation, habitat loss and global climate change. We studied the abundance of 15 migratory shorebird species in a coastal wetland in western India that serves as an important stopover and wintering area by many shorebirds in the Central Asian Flyway. The study site was visited once a week during low tide (from 06:00–12:00 h) for 15 years (2005–2019). Shorebird abundance data was collected following direct count and block count methods. To study the departure of shorebirds we monitored shorebird numbers daily and collected benthic organisms three times a month from the shoreline habitats during low tide. Samples were collected from depths of 15 cm using a metal cylinder from areas that typically had the highest densities of foraging shorebirds. Daily rainfall, relative humidity, temperature of air and water and salinity were measured once a week. Generalized Linear Models GLMs (Gaussian family) was used to determine the variation in shorebird abundance in relation to environmental variables (relative humidity, water salinity, rainfall, water temperature, air temperature), and invertebrate prey abundance. We ran two GLMs with Poisson distribution of error to investigate if departure date varied with environmental variables and the abundance of invertebrate prey. Of the environmental variables, mean air temperature, water temperature and salinity increased significantly during the 15 years while invertebrate prey underwent steep declines. Ten of the 15 species’ declines were predicted by the changes in relative humidity, rainfall, water temperature, air temperature, salinity and invertebrate prey abundance. Departure dates also advanced in several species and were affected by relative humidity, air temperature, water temperature, salinity and invertebrate prey abundance. Our models suggest that salinity and invertebrate prey abundance were driving overall changes in shorebird abundance and departure dates. These two variables were negatively related (invertebrate prey abundance declined with increasing salinity). This was evident throughout the study period, during which salinity increased while invertebrate prey abundance declined. Species declines could be due to poor habitat quality and food availability resulting from environmental degradation. Delays in migration could be linked with inability to find enough high quality food to build up food reserves prior to departure. Better habitat management in key wintering wetlands and stopover sites along the flyway are needed help to restore populations of shorebirds.
ABSTRACT The Indian subcontinent is the primary wintering ground and stopover site for migratory ... more ABSTRACT The Indian subcontinent is the primary wintering ground and stopover site for migratory shorebirds to refuel along the Central Asian and South Asian Flyways. Despite the conservation importance of this region for migratory shorebirds, we lack information on the distribution and abundance of over-summering shorebirds—migrants that remain on their wintering grounds during the breeding season—to evaluate the impacts of anthropogenic change on this poorly understood life history strategy. We conducted weekly surveys of over-summering shorebirds at mudflats, mangroves, and sand beaches at the Kadalundi-Vallikkunnu Community Reserve on the southwest coast of India, 2005–2018. We examined long-term patterns of over-summering shorebird abundance, species composition, and habitat use and estimated proportional changes in over-summering abundance of each shorebird species documented at this globally important site. Over the 14 yr study, we documented 7 over-summering species, including Lesser Sand Plover (Charadrius mongolus), Whimbrel (Numenius phaeopus), Greater Sand Plover (Charadrius leschenaultia), Kentish Plover (Charadrius alexandrinus), Common Sandpiper (Actitis hypoleucos), Ruddy Turnstone (Arenaria interpres), and Pacific Golden-Plover (Pluvialis fulva). Mean abundance and species richness were higher at mudflats than at mangroves and sand beaches, with fewer individuals and species observed over-summering after 2010. Mudflats also had the highest species diversity and evenness compared to mangroves and sand beaches. Management plans that aim to restore vulnerable mudflats and mangroves and to reduce anthropogenic threats such as sand mining and waste dumping are needed to prevent the loss of important over-summering, foraging habitat for migratory shorebirds in southern India and along the Central Asian and South Asian Flyways.
The first case of breeding of the Glossy ibis Plegadis falcinellus in Tunisia has put the seal on... more The first case of breeding of the Glossy ibis Plegadis falcinellus in Tunisia has put the seal on several years of regular observations of wintering individual birds in pre and postnuptial periods, in several wetland areas of the country. Few individuals stay during the summer and 20 couples, recently settled at the fresh water reservoir at the Lebna dam near Cap Bon, nested in 2008. This first case of reproduction permitted the description and evaluation of some reproduction parameters observed at the nest site; average fertility, number of eggs per clutch, hatching and mortality rate.
Nine Ardeidae species breed in Tunisia. About 2,500-3,000 breeding pairs breed each year and more... more Nine Ardeidae species breed in Tunisia. About 2,500-3,000 breeding pairs breed each year and more than 12,000 individuals winter. The breeding population includes 8 regular species: Grey Heron Ardea cinerea, Purple Heron Ardea purpurea, Black-crowned Night Heron Nycticorax nycticorax, Cattle Egret Bubulcus ibis, Squacco Heron Ardeola ralloides, Little Egret Egretta garzetta, Little Bittern Ixobrychus minutus and Eurasian Bittern Botaurus stellaris (for the latter species, breeding is certain but no nest has been found). The Western Reef Egret Egretta gularis is a casual breeder. The Great Egret Casmerodius albus is present all the year round but no nesting has been found.
ABSTRACT Scopoli’s Shearwater (Calonectris diomedea) is a Procellariiform endemic to the Mediterr... more ABSTRACT Scopoli’s Shearwater (Calonectris diomedea) is a Procellariiform endemic to the Mediterranean Basin which is considered to be vulnerable in Europe due to recent local declines and its susceptibility to both marine and terrestrial threats. In the 1970s–1980s, its population size was estimated at 57,000–76,000 breeding pairs throughout the Mediterranean Basin, with the largest colony, estimated at 15,000–25,000 pairs, found on Zembra Island, Tunisia. The objectives of our study were to re-estimate the size of the breeding population on Zembra Island, to reassess the global population size of the species, and to analyse the implications of these findings on status and conservation of this species in the Mediterranean. Using distance sampling, we estimated the Zembra breeding population to be 141,780 pairs (95 % confidence interval 113,720–176,750 pairs). A review of the most recent data on populations of this species throughout the Mediterranean Basin led us to estimate its new global population size at 141,000–223,000 breeding pairs. Using the demographic invariant and potential biological removal approaches, we estimated the maximum number of adults which could be killed annually by all non-natural causes without causing a population decline to be 8800 (range 7700–9700) individuals, of which could be 3700 breeders. Although these results are less alarming in the context of species conservation than previously thought, uncertainties associated with global population size, trends and major threats still raise questions on the future of this species. More generally, we show how a monitoring strategy for a bird supposed to be relatively well known overall can be potentially misleading due to biases in survey design. The reduction of such biases would therefore appear to be an unavoidable prerequisite in cryptic species monitoring before any reliable inference on the conservation status of the species can be drawn.
Abstract We studied the reproduction patterns of Squacco Herons, Ardeola ralloides, during 2009–2... more Abstract We studied the reproduction patterns of Squacco Herons, Ardeola ralloides, during 2009–2010. This study was carried out in two colonies located at Ichkeul National Park (37.184992 N, 9.633758 E) and Lebna Dam (36.744161 N, 10.916569 E), in northern Tunisia. We determined the reproductive performance of the species, and investigated the relationship between reproductive parameters and nest characteristics (height and diameter). We registered successful nesting, with mean clutch size of 4.51 ± 0.85 for both years combined. Hatching success was 3.67 ± 1.07 eggs hatched/nest and fledging success reached 3.06 ± 1.28 young/nest. All reproductive parameters varied between years. The diameter and the height of nest had no effect on the clutch size, the initial brood size, or the final brood size at each site. We estimated the body condition index (BCI) and the growth curves of developing nestlings from repeated measurements of body mass, tarsus, head and bill length. The last chicks (rank four) to hatch had lower (BCI) and growth rates than the first, the second, and the third hatched chicks. These results stress the need for further protection measures be undertaken at Lebna Dam. Accessibility to the site should be highly controlled by the managers of Tunisian wetlands.
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