1903 The Green-backed Gallinule 55 



less hesitatingly admitted into the immigrant catalogue, 

 whereas sixteen far more powerful birds are branded as mere 

 escapes. It reminds me of the pennies found in our old tan- 

 covered school gymnasium floor, which never failed to find 

 claimants because so many boys once had one in their 

 custody ! for more valuable and more rarely found coins 

 there were fewer claimants, because such things were less 

 frequently imported to the playground, though coming from 

 the same original mint. Against the probability of the 

 Green-backed Gallinule or Porphyrio having strayed to Great 

 Britain as a voluntary occasional migrant the following 

 objections have been brought forward : — 



1. It is of small range in its natural habitat — less widely 

 distributed even than P. caruleus. 



2. It is a bird of no sustained flight, and most reluctant to 

 take wing. 



3. Intervening countries do not acknowledge or obtain it, 

 nor has it been observed at lighthouses or migrational 

 observation stations. 



4. Many of these birds are annually imported, and this of 

 all birds is, on account of its climbing powers and deceptive 

 bulk, most difficult to " stow" or confine. One at least has 

 been claimed as an escape. 



Let us digest these objections in order. 



In the first place, there is no inherent impossibility in any 

 bird that can fly for its occurrence in Britain, however 

 circumscribed its natural geographical area may be. From 

 unknown causes birds sometimes, at first suddenly and then 

 regularly, extend their range both for purposes of breeding 

 and autumn migration. On a small scale such an extension 

 has taken place in our own islands within recent years 

 amongst Nightingales in spring and Green Woodpeckers in 

 autumn. The 1888 visitation of Pallas's Sand-Grouse was a 

 similar movement upon a far larger scale. Moreover, those 

 birds which have the most extensive breeding-range do not 

 necessarily wander at regular intervals to countries or 

 districts distant from their accustomed latitude or longitude, 

 as witness the excitement caused amongst ornithologists by 

 the sudden and unexpected occurrence of numbers of Ruddy 

 Sheldrakes in this country in 1892. 



