At Batumi the exclusion of some species for monitoring appears very strange from a birdwatchers perspective because some may constitute an important portion of the total migration. We repeat here that it is important to realize that monitoring is all about long-term effort and that data on migratory species must always be regarded in an international context! This means that some species will not be eligible to ´monitor´ because of practical difficulties or the value of localized counts relative to breeding numbers or numbers of migrants at other watch-sites.
Two bulk species but only one with priority: Eurasian Honey-buzzards vs. Steppe Buzzard
The Eurasian Honey-buzzard and the Steppe Buzzard account for respectively ± 55% and ± 30% of the total count. The selection process that led to the inclusion of one of them and exclusion of the other therefore deserves some more explanation.
Migration of Eurasian Honey-buzzard typically takes place early in the count season, between 25 August and 10 September. This is a period when we can easily involve students to carry out the very labor-intensive counts. Moreover, from the results of pilot counts conducted resp. 8 and 250 km east of the Batumi transect, we can conclude that the migration corridor through the Caucasus is extremely concentrated along a ca 10km broad strip along the coast. Some hundreds of Honey-buzzards in the inland of the Caucasus is an extremely small number compared to the 400.000+ individuals at Batumi. Also note that a particular advantage of this species is the easiness of recording sex and age classes, which allows a much more complex analysis of population dynamics.
The Steppe Buzzard migrates much later, between 25 September and 15 October. At this time it has proven very difficult to find volunteers for the counts. It is therefore unlikely that conducting a high-quality count will always be feasible for this species. Unlike the Eurasian Honey-buzzard, the Steppe Buzzard migrates over a broad front, with significant numbers(several 10.000´s) recorded at our pilot counts further east. Properly recording their migration through the Batumi bottleneck would therefore require a longer transect, which is logistically very complicated.
The huge difference in migratory route choice between the Honey-buzzard and Steppe buzzard poses very interesting questions for future research. However data collection for answering such questions should be achieved with specific short-term projects (e.g. by extended transect counts) and is not to be included in monitoring protocol.
Levant Sparrowhawk: excludeding a threatened species because problems arise across the whole Accipiter genus
If a project aimed at conservation excludes a range-restricted, rare species like Levant Sparrowhawk which occurs locally in internationally important numbers this demands some further argumentation.
Note above that we included Imperial, Steppe and Greater Spotted Eagle as secondary species because monitoring Lesser Spotted Eagle logically implies the on-site identification of all large Aquila species. If Levant Sparrowhawk would be monitored at Batumi also Eurasian Sparrowhawk should be included in the long-term BRC scheme.
The particular challenge in counting Accipiter species at Batumi is tied to their intermediate migration strategies. Although Levant Sparrowhawk often soars in substantial flocks at high altitude the species still shows great overlap with the Eurasian Sparrowhawk in the sense that many individuals migrate individually and low to the ground. Furthermore, at Batumi the topography of the landscape is particularly complex with mountains reaching to altitudes of >2000m within 10 km from the coast. In combination with Sparrowhawks flying at low altitudes this makes both species particularly difficult to detect during ground-based counts when much of the attention is pointed towards the sky where most of the truly soaring raptors are crossing the bottleneck. Overall the resulting additional count effort required to monitor Accipiters is very high compared to soaring species. Moreover, it should be noted that the threatened Levant Sparrowhawk is recorded in numbers that are of much higher international importance for conservation at the western Black Sea (Bosphorus in Turkey and Bourgas in Bulgaria) and the southeastern Mediterranean (Israel).
Although the choice to exclude Levant Sparrowhawk is ´emotionally´difficult from a conservationists point of view, the arguments above show why this choice is justified, indeed even required, upon objective analysis.