AVIAN GENUS CHRYSOCOCCYX 7 



leave it unsaid or minimize it in their effort to advance what seems to 

 them the best, if not the only, possible arrangement of their data. 



Within the limitations expressed in this preamble, I will now 

 outline what seems to me to have been the past history, move- 

 ments, and differentiation of the glossy cuckoos. The group originated 

 in the Indo-Malaysian area, whence it spread to New Guinea, Aus- 

 tralia, New Zealand, to the islands of the southwestern Pacific, to 

 Burma, Assam, and India, and thence to Africa. The evidence will be 

 presented in the following pages. 



First, I will mention the two major geographical dispersals the group 

 underwent, outlining the reasons for my interpretation. These two 

 great dispersals involved a westward-spreading movement from 

 southern Asia to Africa, and a southern- and southeastward-spreading 

 movement from Malaysia to Australia and New Zealand. The latter 

 was probably much earlier than the former in the history of these 

 cuckoos, but it is not possible to prove this since evolutionary rate of 

 change may have been more rapid in the westward-pushing African 

 stock than in the movement that spread to Australia and New Zea- 

 land. In other words, that the present African members of the genus 

 seem more distinct, more divergent from the ancestral stock may be 

 due to more rapid change in a new environment and may not neces- 

 sarily be an expression of greater age than that evidenced by the 

 lesser degree of morphological change exhibited by the present Aus- 

 tralian and New Zealand portion of the group. 



That there are no glossy cuckoos in Madagascar and the other 

 islands of the central and Avestern Indian Ocean (Comoros, Mauritius, 

 Reunion, Aldabra, the Seychelles, etc.) suggests that the westward 

 spread of this group from southern Asia occurred after the isolation 

 of Madagascar and the Mascarene Islands from Africa in Pliocene time. 

 The additional fact that two of the African species, caprius and 

 klaas, have been found in southern Arabia suggests that a more 

 northern route may have been taken. It is equally possible, however, 

 that these southern Arabian birds may be relatively recent 6migr6s 

 from Africa. Both are known from only a very few specimens — • 

 caprius, indeed, from a single one, from Arabia — but klaas appears to 

 have bred there, according to Meinertzhagen (1954, p. 310). 



Similarly, at the other end of the range of the genus, the fact that 

 the birds breeding in New Zealand (C. lucidus lucidus) and in southern 

 Australia and Tasmania (C lucidus plagosus and C. basalis) migrate 

 incredible distances over the open oceans, sometimes as much as 

 2000 miles, to the Solomon Islands and to the islands of the Bismark 

 Archipelago, suggests a revealing annual retracing of their ancient 

 ancestral dispersal between their present southern and southeastern 

 breeding areas and their original locus of origin. 



