SEEN - SE European Bird Migration Network
Bird navigation model - an inherited program with azimuths and switches - as a theoretical basis to the field cage tests
Przemysław Busse
Bird Migration Research Station, University of Gdansk, Poland

A young bird migrating from the breeding ground to a winter-quarter is so composed problem that we must treat it as a “black box”. If we ringed it in a nest and we have recovery from e.g., Central Africa we know “an input” and “an output”. The question is: how it managed the travel? If we ringed it in the nest and next year we caught it when breeding we still have an input and an output, but the bird performed two travels: so and forth. So, we face with even more complicated system: start the autumn migration (“switch on” migrational activity, “switch on” southward direction) - navigation to the winter-quarter (azimuth of migration, “switch off” migrational activity) – wintering – start the spring migration (“switch on” activity and “switch on” northward direction) – and so on. If the bird has inherited not straight-line navigation it must have in the navigation program additional “switch (es)” when to change subsequent azimuths. If the individual is an interpopulation hybrid it has at its disposal more than one navigation program (with their azimuths and switches) and our problem became even more black “black box”.
We know a little bit what our black box contains – some about physiology of start (e.g., fattening, migrational inquietness), some about orientation cues (visual, magnetic). We know that sometimes directional switch can work improperly so, we observe “reversed” migration. In classic cage experiments the main question was which properties of an environment could be used as the orientation cues. The birds were held in captivity and their environment was regulated, sometimes to a great extent. Experimental birds responded to changing cues, but their status did not changed – they did not move according to their activity.
Within our orientation tests we put the black box into an artificial situation for a short while. The bird is on a real migration stop, but it is tested during a daytime when cut off visual cues useful both for nocturnal orientation and diurnal feeding movements. How far it reacts by switching on other long-distance navigation cues and shows us its inherited azimuth (or azimuths!) and direction? Or it behaves remembering the closest environment? How it response to an experimentator manipulations, actual weather situation, sun etc.?
We want to know from where birds arrive and to where they direct in different localities. But we cannot skip the problems how our black box is constructed and what we really see from collected data.
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