150,000 per annum and are dominated by the Boeing 737 and aircraft of similar design. However there are also quite large numbers of movements involving ...
INTERNATIONAL BIRD STRIKE COMMITTEE
IBSC 24/WP 10 Stara Lesna, Slovakia, 14 - 18 September 1998
IS THERE A BIRD STRIKE SYNDROME? : PRELIMINARY RESULTS FROM AUTOPSY FINDINGS.
Karina Lyne 2, Irene Gassner2, Ray Bolger 1 and Thomas C. Kelly12 1. 2.
Aer Rianta, Dublin Airport, Co. Fingal, Ireland.
Department of Zoology and Animal Ecology, University College, Lee Maltings, Prospect Row, Cork, Ireland. *(correspondence)
ABSTRACT This study investigated the pattern of injuries to birds which were found dead at Dublin Airport, Ireland. Cadavers were deep frozen at the airfield, prior to being autopsied at University College, Cork. An autopsy procedure was developed and the most frequently occurring sets of injuries were identified. Broadly, these involved fractures to the skull, the bones of the axial and appendicular skeleton, the sternal and sternal ribs, and the limbs, as well as trauma to the internal organs. X rays were found to be unnecessary as fractures and other gross injuries were macroscopically identifiable at autopsy. Interestingly, most trauma is seen on the ventral surface of the bird's body. This and other patterns of injury are listed and analysed. The results are discussed in the context of identifying a possible Bird Strike Syndrome. This study established for the first time a framework for the autopsy of bird strike related carcasses. Keywords: Birdstrike syndrome, Identification, Traumatic injury. Autopsy
Objectives The principal objectives of this study are: (a) To identify, at postmortem examination, the pattern of injuries sustained by birds in a collision with an aircraft (b) To establish if there is a classical "syndrome" which permits the ready identification of a carcase as victim of a bird strike. Materials & Methods Study Area This study was undertaken at Dublin Airport which is the Republic of Ireland's largest and busiest airfield. Over 10 million passengers utilised the airport in 1997. Aircraft movements number about 150,000 per annum and are dominated by the Boeing 737 and aircraft of similar design. However there are also quite large numbers of movements involving turbo-propellar-type aircraft, especially the Fokker 50. Autopsy Methods The Bird Patrol attached to the Fire Station at Dublin Airport collected all the avian remains utilised in this study. These were gathered either during routine inspections of the airfield or were extracted from aircraft engines following ingestion. If a birdstrike was reported, details of the type of aircraft involved and its phase of flight were recorded. If a strike was not reported, information regarding the previous aircraft movement operating in the manouvering area is also documented. The specimen was labelled with the date and time of collection, location and weather conditions, and, where possible, the aircraft type, placed in a polythene bag and deep frozen. Post Mortem Prior to the post mortem examination the birds were removed from the freezer to ensure that they were sufficiently thawed. The postmortem then followed a routine procedure, modified from Siegmann (1983). Adjustments had to be made, because the focus of this study was on gross injuries to the body of the bird - commensurate with it having been involved in a bird strike - rather than the detection of infectious disease and associated lesions. Using a scissors an incision was from between the maxilla and mandible to the cloaca removing only the integument at this stage (Fig.2). Incisions were then made through the bones of the shoulder girdle and on either side of the sternum midline through the pectoralis major and minor muscles (Fig.3). The sternum and the sternal ribs were then severed which exposed the thoracic and abdominal cavities. The different organ systems were then carefully examined and any abnormalities recorded. A detailed postmortem report was completed for each individual bird examined (Appendix 1). Data Analysis For the purposes of this study the broad anatomical categories, listed below, were utilised. Specific terms follow Procter and Lynch (1993). The Skull = skull fractures and decapitation but excluding minor surface lesions and bruising to the head. The Axial and Appendicular Skeleton = the avian skeleton excluding the skull, the sternum and sternal ribs, and the wings and legs. The Sternum and the Sternal Ribs. The Limbs = the skeletal structures of the wings and legs. The Internal Organs = the organs of the thorax and abdomen excluding the urogenital and nervous systems while including the brain. The Thorax = Ventrally, the region from the base of the neck to the posterior extremity of the pectoralis muscles. The Abdomen = ventrally, the area directly posterior to the thorax extending to the cloaca. The analysis of the data utilised Minitab - Release 10 Xtra. Minitab Inc. The Chisquared significance values were checked against a table (Thompson, 1941).
Fig.1. Manual examination for fractures of wing bones
A total of 92 birds were examined in this study. The largest single group are the gulls (Laridar; n=35). All species of gulls (i.e. Larus ridibundus, fuscus and argentatus) have been pooled for the purposes of this analysis. Likewise with the Columbidae (pigeons and allied forms; n=18); the data from the sample of domestic Rock Doves (Columba livia var domestica) has been integrated with that of Wood Pigeons (Columba palumbus). Some small passerine species were also autopsied including the Skylark (Alauda arvensis), Meadow Pipit (Anthus pratensis) and Swallow (Hirundo rustica). In all, approximately 160 more or less discrete injuries were identified in the total of 92 cadavers that was subjected to post mortem examination. This means that that in excess of 10,000 data points have compiled so far, during this ongoing study. However, for the purposes of this paper it has been decided to present a preliminary outline of the results in which the main trends are identified. The null hypothesis The assumption at the start of this study, and in the absence of any comparable baseline data, was that the injuries to each of the defined areas of the body would be randomly distributed within the sample. The null hypothesis, therefore, is that there is an equal chance of injury to each of the specified broad anantomical regions of the cadaver. This analytical approach may be too general. For example, each of the body regions is not of equal size and some are perhaps more likely to be injured (e.g. the limbs) than others. Nevertheless, in keeping with our objective to identify the general trend in the data set, Chi squared tests were performed to establish the statistical significance of any deviations from the expected pattern. General Injury Patterns In All Birds Skull Skull Damage Fig.4 shows the pattern of injury to the avian skull in the total sample of cadavers. It can be seen that approximately one third of the birds examined suffered palpable injuries to the skull and head (n= 34; 37%, Fig. 4). This means only a minority of birds exhibited identifiable damage (including complete decapitation) to the head and cranium. This proportion is less, but not quite statistically significantly less (x2=3.749, df = 1 p
