SEEN - SE European Bird Migration Network
Experiments
Fig. 1. The experimental stand. Photo: M. Nowakowska

Fig. 2. Putting-on the foil on orientation test cage

Fig. 3a. Counting the scratches on the foil

Fig. 3b. Counting the scratches on the foil. Photo: M. Nowakowska

Fig. 4. Noting the results of an orientation test

Fig. 5. Orientation tests - the data form

Directional preferences of nocturnal migrants
The new method of studying directional preferences in nocturnal migrants includes a new field technique and pays special attention to the inconsistency of directional behaviour pattern in an individual bird. It may be used under real field circumstances, by professionals as well as amateurs: the equipment is simple and cheap, the technique easy to learn in a standardized form. In addition the experiment routine allows collection of big amounts of data since tests may be performed in both night and day. Diurnal tests under an overcast sky have the same value as tests done with good sky visibility, which is not the case in nocturnal tests. Analysis of local vectors in a directional behaviour pattern seems to be of use in the studies on local migratory directions and the overall population composition of migrants.
The experimental stand (Fig. 1). The place of experiments should be a flat area, top of a hill etc., without trees, wires, poles, that may be seen by a bird above the protecting screen.
The experimental routine. Tests can be done at any time, both night and day. There are meteorological limitations, however; tests should not be done with rainfall or snow nor with wet fog causing, condense on the foil of the experimental cage. With wind force exceeding 5° Beaufort experiments are not recommended.
Caught birds can be tested immediately after catching and ringing or kept in not transparent bags or cages for at most two hours.
  1. Preparation of the cage for the experiment (Fig. 2) includes covering its vertical side wall with a stripe of a foil from a roll of width adjusted to the height of the cage, (with an extra 2 cm for folding): fix the beginning of the stripe to one of vertical wires of the cage by transparent sticky tape, then cover the side of the cage with straightened foil, fixing its upper end, finally cut the stripe off the roll after connect the ends. The foil should be carefully handled to avoid making scratches, holes etc. which could subsequently be taken for the signs of bird activity. The cage may be prepared in advance, but longer storage of the cages in a moist air is not recommended as the sticky tape used to fix the foil may come loose.
  2. Locate the experimental cage at the centre of the protecting screen with one of the wires directed to the North (indicated by a previously fixed pole outside of the screen, not visible to the bird). It is handy always to direct the wire where the foil stripe is fixed to the North; this protects against wrong identification of sectors when noting the results.
  3. Transport the bird to the experimental stand in a not transparent bag or cage, remove it and put it into the experimental cage inside the screen protecting it from seeing landmarks. The direction from which the bird enters the cage does not seem to influence the results, but the custom of putting it from one side (e.g. always from the south) could be a rule. After entering the bird the observer should leave the place quickly, note the time (precision 1 minute) and after the agreed experiment time (10 minutes proposed as standard) quickly return and remove the bird from the cage. lf the bird is earmarked for other experiments it must be caught by hand (which is not too easy and many escape). During the experiment time the bird should not be disturbed by sudden noises or things coming into visibility. When larger birds as thrushes are tested, the cage should be fixed to the ground to avoid that the cage is upset by their fluttering.
  4. After the test the results of the experiment should be noted. Count signs of the bird activity sector by sector. Starting always from NNW direction is convenient when you handle the cage with its bottom side to your belly (Fig. 3a and 3b). Count the signs of activity – holes and dots made by bill as well as holes and scratches made by claws of bird when it hopped against the foil. Sometimes these signs of different origin are not easy to separate, so counting them altogether is the best solution. The behaviour of the bird in a cage is to some extent species specific and in one species bill signs are more common, while claw marks are in majority in another. Some practice is needed, but individual differences between observers, if they do exist, concern the number of counted signs and not their distribution. Every counted sign must be instantly marked with colour marker to avoid double counts. It is a good custom to write numbers on the foil first and then rewrite them into the form. Note that, if you handle the cage as recommended above, the correct direction of writing into the form is the opposite (Fig. 4). Longer storage of cages before counting is not recommend because of a danger of unstuck or accidental damage of the foil. However, as it easier and quicker to count the signs made by the bird in good light conditions, cages from the night experiments may at least be stored till next morning (if there are enough cages for all planned experiments). Used foils cannot be handled or stored after removing them from the cage.
  5. Filling up the experiment form (Fig. 5) includes the filling of a couple of boxes with information complementary to the main data: Species, Ring no, Status (A – freshly ringed, first test, B - next test...; R - retrap), Sex/age, Fat score, Date - hour of catching, Experiment time (from- to, given as hour and minutes), Day/night (D, N), Sky visibility (0- none, l - small: cloudiness 7 to 9, 2 - medium: 4 to 6, 3 - good: 0 to 3), Sun/Moon (S - the Sun, M- the Moon visible, ,,-“ none of them), Wind direction (accuracy to 1/8 of the wind-star; 0- no wind), Wind force (0- no wind, 1 - 1° to 2° Beaufort, 2 - 3° to 4° B, 3 - over 4° B).
The existing input software is adapted to specified set of additional data.
After filling up the experiment form the foil is removed from the cage and the cage may be prepared for the next test. One single person working at one experiment stand may without problems handle six birds per hour (included: count of results and preparation of cages) if the experiment stand is not too far from the station. Working at two stands requires some help from a second person serving with the birds.
Created by Pronetix 2006