Floating rafts as breeding habitats for the Common tern, Sterna hirundo. Colonization patterns, abundance and reproductive success in Venice Lagoon

The Venice lagoon hosts the 15% of the entire Italian breeding population of Common terns, Sterna hirundo, highlighting the great value of the area for this species. However, in the last 25 years, a substantial decline of Common terns has been detected in the Lagoon, which culminated in 2008. The main causes of this negative trend were the loss of salt marsh habitats, where terns typically breed in the Venice lagoon. This was due to the increase in the mean sea level and the greater frequency of high tides during the reproductive period with consequent flooding of their breeding sites; competition with yellowlegged gulls (Larus michahellis), predation and human disturbance. As a preliminary experimental approach to counter the depletion of the species and favour its recovery, we performed a habitat loss compensation project by setting up four floating rafts (3x2m), covered by two different types of substrate (sandy and vegetal substrate). This was to function as an artificial nesting site safe from flooding, positioned in a protected internal wetland area of the Venice lagoon, Valle Averto (Sourthern Lagoon). We studied the colonization patterns of the rafts and the reproductive success of Common tern breeding pairs during the 2014 and 2015 breeding seasons. We also investigated those environmental and structural variables that could favour the use of the rafts and the nesting success of the species. In both years, the rafts were successfully colonized and used by terns for nesting. Our results also indicated higher temperature, lower rainfall and greater distance from the shore as the main habitat factors favouring the occurrence and the reproductive success of the breeding pairs, while a windrow of dead plants was indicated as the preferred substrate for covering rafts in order to make them more attractive. The results provided some suggestions for successful restoration plans to be developed in similar lagoon areas

A Land-Use Perspective for Birdstrike Risk Assessment: The Attraction Risk Index

Collisions between aircraft and birds, birdstrikes, pose a serious threat to aviation safety. The occurrence of these events is influenced by land-uses in the surroundings of airports. Airports located in the same region might have different trends for birdstrike risk, due to differences in the surrounding habitats. Here we developed a quantitative tool that assesses the risk of birdstrike based on the habitats within a 13-km buffer from the airport. For this purpose, we developed Generalized Linear Models (GLMs) with binomial distribution to estimate the contribution of habitats to wildlife use of the study area, depending on season. These GLMs predictions were combined to the flight altitude of birds within the 13-km buffer, the airport traffic pattern and the severity indices associated with impacts. Our approach was developed at Venice Marco Polo International airport (VCE), located in northeast Italy and then tested at Treviso Antonio Canova International airport (TSF), which is 20 km inland. Results from the two airports revealed that both the surrounding habitats and the season had a significant influence to the pattern of risk. With regard to VCE, agricultural fields, wetlands and urban areas contributed most to the presence of birds in the study area. Furthermore, the key role of distance of land-uses from the airport on the probability of presence of birds was highlighted. The reliability of developed risk index was demonstrated since at VCE it was significantly correlated with bird strike rate. This study emphasizes the importance of the territory near airports and the wildlife use of its habitats, as factors in need of consideration for birdstrike risk assessment procedures. Information on the contribution of habitats in attracting birds, depending on season, can be used by airport managers and local authorities to plan specific interventions in the study area in order to lower the risk.Collisions between aircraft and birds, birdstrikes, pose a serious threat to aviation safety. The occurrence of these events is influenced by land-uses in the surroundings of airports. Airports located in the same region might have different trends for birdstrike risk, due to differences in the surrounding habitats. Here we developed a quantitative tool that assesses the risk of birdstrike based on the habitats within a 13-km buffer from the airport. For this purpose, we developed Generalized Linear Models (GLMs) with binomial distribution to estimate the contribution of habitats to wildlife use of the study area, depending on season. These GLMs predictions were combined to the flight altitude of birds within the 13-km buffer, the airport traffic pattern and the severity indices associated with impacts. Our approach was developed at Venice Marco Polo International airport (VCE), located in northeast Italy and then tested at Treviso Antonio Canova International airport (TSF), which is 20 km inland. Results from the two airports revealed that both the surrounding habitats and the season had a significant influence to the pattern of risk. With regard to VCE, agricultural fields, wetlands and urban areas contributed most to the presence of birds in the study area. Furthermore, the key role of distance of land-uses from the airport on the probability of presence of birds was highlighted. The reliability of developed risk index was demonstrated since at VCE it was significantly correlated with bird strike rate. This study emphasizes the importance of the territory near airports and the wildlife use of its habitats, as factors in need of consideration for birdstrike risk assessment procedures. Information on the contribution of habitats in attracting birds, depending on season, can be used by airport managers and local authorities to plan specific interventions in the study area in order to lower the risk

The abundance of yellow-legged gulls Larus michahellis breeding in the historic centre of Venice, Italy and the initial effects of the new waste collection policy on the population

The yellow-legged gull Larus michahellis has undergone widespread colonization of the urban environment in the recent past. The first urban breeding gulls were recorded in the historical centre of Venice, Italy, in 2000, and by 2005 there were already 24 roof-nesting pairs, with this number increasing significantly over the last decade. In 2016, a new door-to-door garbage collection system was introduced in Venice to prevent the accumulation of rubbish in the streets and limit the trophic resources available for the species. This study provides an up-to-date estimate of the Venice yellow-legged gull urban population using distance sampling method. We also studied the effect of the new waste collection system on the species by comparing the population estimate before (2017) and after (2018) the full implementation of this change and by analysing the trend of individuals collected in the old town by the wildlife recovery service during 2010–2018. Results estimated ca. 430 breeding pairs in June 2018 showing a 36% decrease with respect to 2017. We also found a decrease in the number of 1-year-old birds and pulli collected by the wildlife recovery service starting from 2016, when the policy implementation began. Our data did not show a significant decrease in the overall number of individuals, suggesting that the new policy has a stronger effect on the breeding success of the species than on adult survival. This study emphasizes the importance of preventing rubbish accumulation in the streets as factor for reducing the abundance of urban yellow-legged gulls

Melatonin reduces migratory restlessness in Sylvia warblers during autumnal migration

Abstract Introduction: A remarkable aspect of bird migration is its nocturnality, particularly common in Passeriformes. The switch in activity from purely diurnal to also nocturnal is evident even in caged birds that during migratory periods develop an intense nocturnal restlessness, termed Zugunruhe. The mechanisms that control this major change in activity are mostly unknown. Previous work with Sylvia warblers suggested an involvement of melatonin, a hormone associated with day-night cycles in most vertebrates. In a recent study we found no effects of melatonin administration on Zugunruhe during spring migration. However, previous studies indicated that the response to melatonin manipulation could differ between spring and autumn migration, which are in fact separate life history stages. Here we tested whether a non-invasive treatment with melatonin can alter Zugunruhe in wild garden warblers S. borin and blackcaps S. atricapilla subject to temporary captivity at an autumnal stopover site. Food availability in the cage (yes/no) was added as a second factor because previous work showed that it enhanced Zugunruhe. Results: The melatonin treatment significantly decreased the amount of Zugunruhe, while the availability of food only tended to increase the amount of Zugunruhe. Fuel deposits also had a strong effect on the amount of nocturnal activity: lean birds with a fat score of 1 showed significantly less Zugunruhe than fatter birds. The change in body mass during the time spent in the recording cage depended on food availability, but not on any of the other factors. Conclusions: This study shows that the migratory programme of two Sylvia warblers can be manipulated by administration of exogenous melatonin and confirms that this hormone is involved in the control of migratory behaviour. To our knowledge, this is one of the first demonstrations that the autumn migratory programme can be altered by hormonal manipulation in migrating birds. The comparison with a similar study carried out with the same modalities during spring migration suggests that there are seasonal differences in the sensitivity of the migratory programme to hormonal factors. In birds breeding in the northern hemisphere, the importance of a timely arrival to the breeding sites could explain why the control of the migratory programme is more rigid in spring

Indicator variable I which determines whether or not the fifteen groups of species could reach the altitude at which aircraft fly when at 3, 8 and 13 km buffer from the runway.

<p>Indicator variable I which determines whether or not the fifteen groups of species could reach the altitude at which aircraft fly when at 3, 8 and 13 km buffer from the runway.</p

Area within 13-km buffer from Venice Marco Polo airport (VCE) divided in 1-km² cells grid and habitat categories present in it.

<p>Land uses were identified using CORINE Land Cover, CLC, classification and mapped using a Geographical Information System, GIS.</p

ARI computed for Venice Marco Polo airport (VCE) in the period 2006–2011 compared to birdstrike rate per 10,000 aircraft movements.

<p>A clear seasonal pattern of the ARI risk index is visible, with higher values in late summer months. A significant correlation between ARI and the birdstrike rate computed for VCE was found (Spearman test, P<0.05).</p

Model selected per group of species and relative number of parameters (K), Log-Likelihood, Deviance explained and loss of deviance explained by excluding from the model a covariate at a time.

<p>Habitat covariates contributing most to attract each group of species are highlighted in bold.</p><p>Model selected per group of species and relative number of parameters (K), Log-Likelihood, Deviance explained and loss of deviance explained by excluding from the model a covariate at a time.</p

Study area with the two investigated airports Venice Marco Polo (VCE) and Treviso Antonio Canova (TSF).

<p>Airports are located in the Northeast of Italy.</p