A new methodology for computing birds＇ 3D home ranges

Background: So far, studies of avian space use are mostly realized in 2 D, with the vertical dimension ignored. We propose here a new, relatively simple and computationally reasonable method for the estimation of volumetric(i.e. 3 D) avian home ranges.Methods: Through accurate GPS data-loggers, we collected 25,405 GPS points on Lesser Kestrels'(Falco naumanni) space use during the nestling period in one main colony in Italy. We applied our 3 D home range estimator to the whole GPS dataset, and also separately to diurnal and nocturnal GPS points.Results: The 3 D colony home range resulted equal to 28.12 km3. By considering daytime and night-time separately, the volumetric home ranges resulted considerably different.Conclusions: Our 3 D home range estimator, because of its intuitive and straightforward properties, can easily capitalize on the datasets offered by modern biotelemetry(data-loggers, light detection and LIDAR sensors) and enhance conservation strategies for mitigating anthropogenic impacts on bird species. Its applications embrace, but are not limited to, more accurate estimates of collision risk with power lines, aircrafts and wind farms, and increased knowledge of birds' space requirements in order to persist in their distribution areas.

A new general index of home range overlap and segregation:the Lesser Kestrel in Southern Italy as a case study

Background:There is increasing interest in evaluating home-range overlap(or,otherwise,segregation)between bird species,and between or within bird populations,to inform spatial planning.So far,studies of home-range overlap typically make use of comparisons between pairs of individuals,populations or species,and return a matrix of pairwise overlaps(e.g.,percent overlaps).However,when the number of individuals,populations or species to be compared is elevated,an overlarge overlap matrix is difficult to interpret from an ecological viewpoint.Methods:We propose here a new,conceptually simple and computationally efficient index(general overlap index;GOI)for the ready computation within GIS of home range overlap of an arbitrarily large number(i.e.,n≥2)of individuals,populations or species.Whatever the number of home ranges to be compared,GOI always returns a single score between 0 and 100.As a case study,we applied our index to 24,074 GPS points of 10 Lesser Kestrels(Falco naumanni)in order to estimate within-colony and between-colony overlaps in two neighboring colonies in Southern Italy.Results:Within-colony overlap was elevated for both colonies(96.41%at Cassano delle Murge,n=5 individuals;81.38%at Santeramo in Colle,n=5 individuals),while between-colony overlap was low(19.12%;n=2 colonies)and,after a randomization procedure,more spatially-segregated than expected by chance.Conclusions:Modern biotelemetry offers huge amounts of data describing the space use of animal species.The use of intuitive and straightforward indices,like GOI,can be useful to promptly extract ecological information from such an amount of data(e.g.detecting change in space use over successive years,evaluating the reliability of various home-range estimators).

Spatio-temporal patterns of the Red-footed Falcon's hunting behavior during the nestling period suggest ad hoc conservation policies

The Red-footed Falcon(Falco vespertinus)is a species of high international conservation interest.We analyzed its hunting behavior at the two largest colonies in Italy during the nestling period.Using accurate data-loggers,we tracked three adult Red-footed Falcons in June and July,2019 and collected 4703 GPS points.We detected clear patterns of hovering and perching activity(HPA)in both time and space.HPA occupied one-third of the Red-footed Falcons’day,and showed two peaks just after sunrise(between 35 and 40%of the monitoring time)and just before sunset(50‒60%)in both June and July,and minimum(20‒30%)at night and during the hottest time interval(10:00 a.m.‒4:00 p.m.).Almost 40%of HPA occurred within 50 m from nests.Our findings,although preliminary,have important implications for the conservation of these two colonies that are located within two Natura 2000 sites.The detected spatio-temporal patterns of Red-footed Falcons’hunting behavior suggests the creation of two nested protection belts:the inner one is a narrow belt(up to 50 m from the two rows of trees that host the two colonies)with integral conservation,and hopefully increase the alfalfa crops and fallow land,and the outer belt(50 m‒2 km)with optimized agricultural activities.