[Open questions concerning the Cuckoo Cuculus canorus 6.] (in German)

Publication Type:Journal Article
Year of Publication:1987
Authors:Thiede, W.

1. Autumn dates of the Cuckoo in North- and Middle-Europe and in the UK are extremely rare. Only 160 October- and 22 November-cases are known in .apprx. 115 years of observation. The Cuckoo thus leaves our area latest until mid-September, 5 cases are reported from England and Wales in December. 2. Only late born and handicapped birds are likely to remain. Late born consequently migrate later. 3. In December as well as in winter (January, February) the Cuckoo is living in areas of Africa with in excess of 50 mm rainfall/month (seel 1984a). In our European reporting-area we have only two observations for February, in England. Between the extreme dates 26. 12. and 4. 2. exist 40 days without any observations of a Cuckoo, before and after many more. 4. There exist 2 summer proofs from Africa, both birds shot on a 6th of June, both in East Africa. The Cuckoo does not oversummer in Africa, even the birds of last year are flying home, though time-delayed. 5. The beginning of calling (kuk-kuk) equate in the literature with the first arrival in spring. At that considerable doubts exist. A difference of appr. 10 days between first arrival and beginning to call is evidently not rare. Caller and noncaller at the "firsts" can be locals as well as passing migrants. 6. Why and how many of the arriving cuckoos are silent for several days, is unknown. Speculations only exist. 7. The majority of the males migrate before the females, but some females migrate as early as the earliest males. 8. The Cuckoo migrates individually or together in groups or in masses. 9. The Cuckoo migrates at day and at night. 10. Social migration with other birds was mentioned so far twice but needs confirmation. 11. The scanty number of victims at beacon-fires on one hand and small number of birds observed migrating in day-time enable us to presume that the Cuckoos fly much higher than expected and beyond the ability of our armed eyes. A migration height of 350 m was once measured when the bird was set free. 12. Cuckoos begin and terminate their migration at any time during day and night. Their migration speed is likely 50-60 km/h. 13. During active migration Falco eleonorae, F. peregrinus brookei and Stercorarius parasiticus are known enemies. Adverse weather, obstacles and beacon-fires are taking their toll. 14. With the end of February calling Cuckoos are known fropm migration in Arabia and Africa. Cuckoos also call during stopovers and rests in Mediterranean countries, as it is known from Malta and Cyprus. The gonades are not developed at this time. 15. Cuckoos also call in active migration in our areas, whether singly or in groups. Other calls than the kuk-kuk were also reported several times during migration. 16. Cuckoos possess and know social bonds of various kinds during migration and rests, from a peaceful being together to fights among males. 17. Cuckoos arriving after a long sea-crossing at .apprx. noon immediately fell asleep and were active only next morning. 18. The animal menu of the Cukoo is more manifold as sofar postulated. Besides insects (and Hymenopterans have to be added) there are earthworms, snails and slugs, frogs and toads and birds, evtl. small mammals, too. The Cuckoo eats complete clutches, not only single eggs. Unresearched are the when and why of this energy-laden menu (in the very first days after arrival eventually?) and the connections between the departure of the ad. in midsummer and the availibility of suitable insect food. From a Danish paper seems it possible to deduct that the ad. depart in a time of temporary shortage of caterpillars. With that they seem to invite the uv. to a rich table. 19. The food of the Cuckoo in Africa.sbd.where by the way all Cuckoos overwinter.sbd.is practically unresearched. According to the few observations available it is resembling the food in Europe. 20. Sofar the pellets of the Cuckoo were neither collected nor systematically examined. 21. The rufous colour morph of the female cuckoo seems to be dependent of the habitat and of the birds of prey which are active in the resp. habitat and of its dnager for the foster-parents. The theoretical models of Voipio (1953) are waiting for a experimental verification in this field. 22. Sofar we know of one geographical area, where the rufous cuckoos appear in a higher percentage in the spring migration: the island of Cyprus. In Malta rufous cuckoos appear only accidentally, from Turkey we lack informations. 23. The occurence of rufous ad..male. is strongly questioned. It might be possible that a retarded moult in immat..male. could simulte its occurence. 24. In the literature the author could find 14 colour-aberrant cuckoos. In the majority they were leucistic variants. Only two were real albinos. The revision of the scattered and largely forgotten records have resulted in the realization that in the questions treated much is still to be done in future. Nearly all questions raised can be handled by field-ornithologists.

Taxonomic name: 
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith