sr li t; t! (, .{' rfigrfr ao c) ,r< U' lt .= .cr (E a o bS o o CL o) E .= = $ lrJ U) m (E :) IIJ o (9 ol o o N o o + o o G) o o o o o (1ee1) sseJc opnlglv t tt o o o t! C) o o 5{4
f< (t) Becker (1996) summarized the discussio. n the Low LevelWG on 'en route b rd st. ke preveniion d!r ng thc last ten years. He is perfectly right in his conclusion that we should hcad lor an lntegrated approach, combi.i.g geographical, b olog cal, weather and radar data . My staremcnr ol today s rhar we on y can make such inte9rated prevention operat onaly stable whef we succeed n classifvino and subsequenty standardislna the d ffc.€nt prevention eements. In olhcr wo.ds: we must develop a.d speak ihe same ang!age in order to communicate abour the .redictab c and non o.edic.r"ble aspects of the bnd strlke risk. Predictab e risks arc in principle open ior.e iiiablc prevenlive measures rcsult ng in a quanrlflab e risk reduction. A!t also the .ema ning .on pr€d ctab o types of b rd danger can be brought under control to a ce(ain extcnt, Remote sensifg of bird movcrncnts has a proven porenrial in rea 1me warning systems (B!urma& Brldeicr 1990, Lcshem 1994). Th s p.per aims ro stim! ate berter comm!n cat on on the mproveme.i of nvoid..cc sysrems by Jocussing on the crillca iss!e ol ow evel bira ilgfr, Evidence from military stalistics (, o o B rd control at the runwav itself is a ready s!ccesful ai many airporrs. Less wde spread, and llmred ro mi(ary aviation, b!r techn cally speakng ripe for mprovement, are large sca c warning sysrems ndic.ri.a mass b rd migrario. n h gher airlayers. However, the 'bonom l]p'a.d 'lop.down'approach rogerher do by f.r not solve all bird strike problems. A gcographicalcomparlson ol rhe (low levc ) altitude disrribution of mllilary bird strikes from EUFBASE indrcares a s!bstantial p.oblem, jusr outside visual range but .lso below lhe coverage of mosl .adars: iigure 1. Thls risk is posed by loca b rd f ights over up to sorne tens of kilometers, especia ly n coaslal and wcaand arcas. <strong>Bird</strong> srrikes may i.dic.re rhe yeat rcLn.l avercge anitude disrriburron oi bnds (almost) inespective ol the time spend and disrance covered by ai.cratt €t d llerent he ghts. Th s s on y thc casc whcn wc sclccl so ca led 'local strikes e.g. d!rlng Iake off, landrng and overshoot (Buurma 1984), D!rlnlt these ilghl phases the 1i!ht path oi the :i.craft has a lixcd ang c 1{) the ea(h s!riace. The Europea. Miirary B rd St ke D.iab.se (EURBASE, see also Bu!rma & Dekker 1996) olfcrcd thc posslb lity to compare this selecrion (N=2582) lrom iive wcst-c!ropean ai. lorces, In f g!rc 1 wc f ttcd curves rhrou!h the a t tudc dlsrribuio.s in 100 ft classes. The resu rs look .ather slmular, bul when we nspecrhe curves closer i.e. at 3o0 it (ca 100 m) and comparc the rwo exvemes, GAF and BAF, we f nd thal the UK birdsrrikes at thls hcicht are rhree timcs mo.c frcquenthan thosc ovcr Gcrmany. The concluslon is therctorc that ihe FAF nol only suffcrs trorll a h gher bird slr ke rate (see Bulrma & Dekker 1996), blt las the curves are percentua ) a so from a d lferenl lype ot risk than the GAF. Appareft y the blrd popu allo. aDove and <strong>aro</strong>und the British lsles, which ls domlnated by coasrar and wel and species, fles hi!hcr and ai a larger \43