Description of the study area
Bahir Dar International Airport, established in 1954, is one of the International Airports in Ethiopia located 8 km to the West of Bahir Dar City, the capital of Amhara National Regional State. It is geographically located at 11°36′30″N latitude, and 37°19′30″E longitude at an elevation of 1821m a.s.l (Fig.2). Its main runway length and width are 3100 m and 45 m, respectively. The Airport and its surrounding area is dominated by grassland, bushland, wetland and modified habitats. There are a lot of tourist attraction sites around the Aairport including ancient monasteries and churches on the Islands of Lake Tana. Furthermore, the Airport’s scenery with the Lake Tana and roads in the city create great pleasure to the travelers.
Ten years rainfall and temperature data of the study area showed that the highest average monthly rainfall was 391.92mm July and the lowest was 1.02mm during January, and the average monthly minimum and maximum temperatures were 6.46 °c during January and 31.87°c during April, respectively .
The study area was stratified on the basis of its habitat types, and the sampling unit within each habitat type was determined based on vegetation type, structure and the corresponding area coverage. As a result, the area was classified into four habitats namely bushland, grassland, wetland, and modified habitat. Among the four habitat types, three of them such as bushland, grassland, and modified habitat are found inside the airport whereas the wetland is located immediately outside the Airport towards the direction of Lake Tana. Line transect and point count methods were used to study diversity and relative abundance of birds  in and around the Airport.
Line transect method was used for relatively uniform areas of wetland and grassland habitats since the areas are open, while point count method was implemented in the relatively dense bushland and modified habitats . Sampling plots and blocks were established for point and transect count methods, respectively. The number of sampling plot and blocks were determined according to the size and type of vegetation cover of the study habitats. The approximate width and length of the transect was on average 50m and 200m, respectively. Transects were separated from each other by 100m, and a total of 10 sample blocks (each comprising 5 transect lines), and 11 sample plots (each comprising 5 sampling points) were used in the densely vegetated habitat.
Bird-aircraft strike incidents and methods of its prevention were assessed by interviewing 26 respondents (23 males and 3 females) among 100 officers and field workers selected using purposive sampling method. Selection of the respondents was made based on the basis of relevance and relatedness of their duties to bird strike control activities in the study area.
Point count method was used to collect data in the bushland and modified habitats, whereas transects were used in the wetland and grassland habitats. During point count method, suitable sites were chosen and birds were identified and counted from a fixed position within a circle of 25m radius for specific period of 10 minutes at every point. All birds seen and heard within this 25m radius were recorded. To minimize the disturbance during counting, a waiting period of 5 minutes prior to counting was applied.
Using the transect count method, birds were counted by walking at 2km/h and uniform pace throughout the whole transect. However, sometimes the speed of walking on the routes was determined by the number of birds present and the extent of difficulties in recording them.
Dry season data were collected from February – April 2020, and data for the wet season were collected from June – August 2020. Census data for both the dry and wet seasons were collected twice a day when most birds are active early in the morning (6:30-9:00 a.m.) and late in the afternoon (4:00-6:30 p.m.) for five days per month with a total of 150 survey hours during the whole study period.
Field observations were made to identify birds at species level using binocular of magnification power 10 and objective lens diameter of 50 (10 x 50), species identification were carried out using appropriate field guide book, and photographs were taken for further identification of birds. Movement pattern of birds that usually cross the runway was studied to evaluate the problems of bird to aircraft strike. The time of the day when the bird flight was the highest and activities performed by the birds such as flight direction and flock size were also recorded.
Structured interviews were employed to collect the required data to assess the status of bird-aircraft strike problems and their control methods applied in Bahir Dar International Airport. Secondary data on bird strike incidents were collected from Civil Aviation Authority Office, Bahir Dar Branch.
Association of birds and seasons with habitat types were analyzed using Chi-square test, and one way Analysis of Variance (ANOVA) was used to check the mean abundance of species difference among the four habitat types and between seasons. Moreover, bird species diversities in each habitats of the study area were calculated using Shannon-Wiener diversity (H'), and evenness (E) indices.
Shannon Wiener diversity index is calculates as:
H' = - Σ Pi × Ln (Pi)
H' =Shannon-Wiener diversity index
Pi = the proportion of each species in the sample
Ln (Pi) = natural logarithm of this proportion
Species evenness is by Shannon’s equitability index (E) which is calculated by:
E= Shannon-Wiener evenness index
H' = Shannon-Wiener diversity index
Hmax = lns
Ln = Log normal
S = Total number of Species
Simpson’s similarity index (SI) was also used to evaluate the similarity of species between two different habitats in both seasons using the following formula:
SI = 2C/A+B
SI= Simpson’s similarity index,
A= number of species that occur in habitat ‘A’
B= Number of species that occur in habitat ‘B’
C= Number of common species that occur in both habitat ‘A’ and ‘B’.
The relative abundance of bird species in each habitat was calculated by:
n = Number of individual species
N = the total number of individuals of all species
Relative abundance values were used to ordinarily categorize each species under the following five abundance categories  (Table 5).