Colour Marking of Common Cranes in Europe
First Results of the European Database

( Published in  Vogelwelt (1999) 120: 295-300 )

Javier A. Alonso
Dept. Biología Animal, Facultad de Biología, Universidad Complutense, 28040 Madrid, Spain
and Juan C. Alonso
Museo N. Ciencias Naturales, CSIC, José Gutiérrez Abascal 2, 28006 Madrid, Spain

Colour marking of Common Cranes in Europe: an introduction

Marking of Common Cranes (Grus grus) in Europe with individual three-colour codes was proposed for the first time during the meeting of the European Crane Workgroup in Hungary 1985 by the Spanish Working Group, after having been preliminarily discussed during the III International Crane Workshop, India 1983. The goal was to start with colour banding during the "Crane hard work year 1988".

However, between 1985 and 1988 a total of 23 young were banded with red alphanumeric bands in Sweden, Finland, Latvia and France. Observers have experienced that these bands could be read only occasionally, particularly at wintering localities, where cranes are relatively difficult to approach. Therefore, J.A. and J.C. Alonso again proposed during the II European Crane Workshop, Estonia 1989, the definite change to 3-colour codes. This system was finally adopted after voting by representations of the different countries (Van der Ven 1995). Nevertheless, Finland and Sweden continued banding with the alphanumeric bands up to 1992, (a total of 62 young), and even one young was still banded with this sistem in 1995. The new scheme for individual colour marking was published in 1990 (Alonso & Alonso 1990). In Spain colour banding started from the very beginning -March 1988- (Alonso et al. 1995) with the three-colour system, which is currently being applied all over Western Europe.

In January 1994 the European Crane Workgroup held a round table on colour banding at the International Crane Conference in Orellana (Spain). All the marking groups (Finland, Sweden, Germany, Poland, France, Spain and Portugal) were represented and did agree to ask all crane ringers to follow banding rules established by the ECW at Tallin in 1989. First, that all cranes banded as young near the nest would carry a long band (its colour indicating the country of origin) on the left tibia and a three-colour individual combination on the right tibia. Country colours for the long bands were: Sweden: red; Finland: yellow; Germany: light blue; Norway. orange; Poland: green; Russia: white.

The birds banded at wintering or staging areas would only have the three-colour combination on the right tibia (some birds may also carry a radiotransmitter attached to the left tibia). A few individuals have been banded by mistake with the long country-colour-band on the right tibia and the individual combination on the left. In any case, the ECWG decided not to consider the possibility of using a given 3-colour-combination for 2 different birds by means of using alternatively both tibias. This means that, once a given 3-colour-combinations has been used on a bird on its right tibia, that combination cannot be used for another bird on the left tibia. The reason was avoiding possible mistakes of right/left tibia in reports.

When all possible individual combinations would be exhausted in natal areas, as already happened in Finland, the country-long-band would be substituted by a three colour band keeping the top and bottom rings of the country colour, e.g. Finland was then starting again with yellow-red-yellow --instead of the long-yellow band-- plus the individual combination; next should come yellow-black-yellow as the country colour, and so on. Sweden will in the future change the long-red band to red-white-red, when all three-colour-combinations with long-red are exhausted. Germany should change the long-blue band to blue-white-blue. Therefore the following individual combinations are not to be used in any country, as they are reserved to substitute the country-colour-long-bands in the future: Yellow-Red-Yellow and Yellow-Black-Yellow, for Finland; Red-White-Red, for Sweden, andBlue-White-Blue, for Germany.

It was also decided that the Spanish Working Group would continue coordinating the data-base in Europe, providing the colour bands for Germany, Poland, France, Portugal and themselves, and elaborate a report on colour banding results to send it to all members of the ECWG. The Finnish Working Group would provide colour bands for Sweden, Norway and themselves, and would therefore take care to avoid possible mistakes in the codes distributed to these countries.

The ECWG also elaborated some recommendations to facilitate the reading of colour bands by observers not used to colour banding of cranes, and to make easier, or even possible sometimes, the identification when the reading is not sure:

a) Never put two rings of the same colour together (e.g. Blue-Blue-Red)

b) Be careful when using the metal ring; its position (tarsus vs. tibia, left vs. right) could be the cue to discriminate between two similar alternatives in some dubious readings. Write the true position of all the rings and check it carefully before releasing the bird. Don't hesitate to communicate banding errors (every bander will eventually make some mistake, it is only a question of time and the number of birds banded).

In case of any doubt, or should any modification to this scheme be introduced, ringers are kindly asked to contact Dr. Javier A. Alonso, prior to make any individual decision, in order to avoid mistakes.


The data-base of colour banded Common Cranes

A first draft compiling all available data of colour banded cranes in Europe (Russia excluded) was prepared by J.A. and J.C. Alonso and distributed to all members of the ECWG. Many mistakes have been corrected, and others will be corrected in future versions, to be sent to the country groups.

The data-base for every different country includes (a) first old only-metal-ringed cranes, where information was available; (b) alphanumeric bands, listed in alphabetical order, and (c) the three-colour-coded individuals, in alphabetical order of colour code. To simplify the data base we only included as separate records those contacts from distant dates (when they are from the same locality) or from different areas (by the coordinates). Contacts from the same locality in different days within a short period are related to as "also seen on...", or "also seen from... to ..." in the COMMENTS field. This was done for instance to include in a single line (record) those contacts for a whole wintering period in a single Spanish locality, or for a prolonged period during summer gatherings in Finland or Germany, or for a staging period in a single locality during migration). We also summarized multiple contacts from a single day including them as a single record, even if they were up to 20 km apart, to avoid e.g. unnnecessary complicated records of radiotracked birds during their wintering in Spain.

Fields L-TIBIA, R-TIBIA, L-TARSUS, R-TARSUS indicate the four possible positions for both the colour or metal rings, or for leg transmitters. In all the data-base alphanumeric bands are mentioned as "RED-..." plus the alphanumeric code (e.g. RED-P35), and long country colour bands as YELLOW-long, RED-long or BLUE-long. Colours are always referred to with the following letters: White= W, Black= Bk, Green= G, Blue= Bu, Red= R, and Yellow= Y.

The word "metal" in one of these fields indicates the position of the metal ring when the observer did report it. Any data in parenthesis indicate that some doubt still persists (e.g. the number of the metal ring, or the word "metal" in parenthesis mean that we still don’t know if the metal ring is on left or right leg, although the observer did report a metal ring). Several dots or question marks mean that some data are still missing.

The field LOCALITY states the locality reported (between parenthesis the Kreiss, Land, deparment, province, etc. and the country). Some of them are still missing or incomplete, and country coordinators are kindly asked to complete them. LATITUDE and LONGITUDE have been indicated were ringers/observers indicated them, but have not been filled in systematically but in Spain. We kindly ask the country crane groups to fill up their own country coordinates (either UTM system or geographic -degrees and minutes-).

The field RINGER/OBSERVER contains the abbreviated name of all people involved in every record, and a complete list of ringers and observers is included at the end of the data base. Parenthesis indicate here that the person who reported the data was not himself the observer, but it was another unknown person who observed the crane.

The field COMMENTS includes any relevant information on every observation. The text in inverted comas is a literal citation taken from the observers’s report.


Preliminary results from Common Crane colour banding

General remarks. More than 331 cranes have been colour banded up to now with the three-colour system, including all the birds banded until 1996, in Germany and Spain, but only those banded up to 1994 for Sweden and Finland (see Table 1). These banded birds have produced, until autumn 1995, 253 different records of individual cranes, although some of them may include, as already explained, many contacts from succesive days. Nevertheless, some alphanumeric bands have also been read, but almost all of them belong to only a few very special localities/observers, such as Tammela (Finland) and Laxa or Hornborga (Sweden) for example. The probability of reading alphanumeric bands, is less than 10% of those seen (own data). Therefore, they are not useful -and haven’t been included- in the analysis of results because they are not equally readable.

Table 1 also shows the mean number of observations per bird, considering only birds contacted at least once. The percentage of individuals observed at least once is maximum for Finnish cranes, probably due to the fact that most young are controlled a few days after marking close to the ringing site.

Table 1. Results of Common Crane 3-colour banding

 (1) Including only birds banded until 1994

The resighting probability is better shown by the number of birds contacted more than once after banding. The percentage is then maximum for birds marked during the winter in Spain, due to (i) the relative lower mortality of juveniles banded when they are already grown in winter, and (ii) the fact that winter banding includes a high percentage (60%) of adult birds. With respect to the mean number of contacts per individual bird, it is again very similar for Finnish and Spanish banded birds if referred to all the birds contacted at least once (last column in Table 1), but is higher for the Spanish cranes when the individuals observed only once and close to the ringing site are deleted (i.e. % cranes contacted 2 or more times). Perhaps the best way to evaluate the results of colour banding would be to consider the number of migratory trips made by the cranes after being banded (Table 2). The high percentage of contacts with Spanish cranes does again reflect the effect of the higher survival probability of adult birds in this sample.


Table 2. Number of migratory trips made by individuals contacted at least once after leaving the country where they were colour banded

(1) No. of trips is exact for cranes banded as young (i.e. in Finland, Sweden, Germany or  juveniles in Spain), but is a  minimum for Spanish banded adult cranes, as all of them have already done at least one trip to come to Spain before being banded in winter

Some life history parameters: Age of pairing. According to preliminary data, cranes seem to pair during their fourth year. There are some birds which were banded as young during their first winter, and have been seen afterwards paired when adults. It should be remarked that the five examples we have (individuals Bu-W-G, G-W-Y, W-G-W, Y-G-W and Bk-Y-Bu -the last banded in France-), were all seen paired for the first time four years later. Also a German bird (N43) was first seen paired during its fourth winter, and a Swedish one (F36) when four years old.

Age of first successful breeding. There is only one record of a crane banded as young in 1989, that has been later (spring 1996) seen with their own young, thus we should wait for a larger sample to conclude about this parameter.

Breeding success. Data on productivity of known birds are very scarce. There are only three birds whose breeding success has been ascertained along more than 2 years (W-Bu-W, Y-Bk-G and Y-R-Bu), and their success in different seasons was 0+1+1+0+1, 1+2+0+1+2 and 1+0+1 young. Careful observations on pair and breeding status of marked cranes should prove very useful in the future.

Change of mate. There are at least four evidences of adult birds banded in winter together with their families (individuals, Bu-W-Bu, Bu-Y-G, and R-G-R), that have been seen years later without their colour marked mates, although the latter were not seen any more (i.e. probably died). For instance, Bu-W-Bu was mated with Bu-W-R when banded in 1991: they had two young: In 1992 and 1993 they didn’t succeed in breeding any young, although they were still together, but in 1994 and 1995 the bird was seen paired with an unmarked adult and with one young in each of both years. Bird Bu-Y-G bred one young with adult Bu-R-G in 1991. Next year, still paired with the same adult, had no breeding success. Afterwards was recognized as a female during mating with an unmarked bird in 1994, but seen unpaired that winter, and in winter 1995 was again seen paired without any young. There are some more examples of birds banded together with their mates and seen some seasons later without their mates. On the contrary, there are also some examples of birds contacted along several years always with the same mates (individuals R-Bk-R, Bu-Y-R, and R-Y-W), some of them up to four breeding seasons with the same mate.

Return to the same breeding/wintering place. Birds probably return to the same area where they were born, although there are still few data on cranes banded as young and later seen breeding (the German N32 was seen nesting at ca. 2 km from the nest where it was hatched)(Mewes & Nowald, pers. comm.). But, to what extent is this true during immature period? There is at least one example of two Swedish birds (W-Bu-R and W-R-Bu), born respectively in 1992 and 1993 in the same area. They spent winter in the area, where they were seen together several times. They are not siblings of the same year but is it possible that both of them were born in the same nest in successive years?

Return to the same wintering area. There is already enough evidence that some individuals return to the very same place to winter year after year. Indeed, some of them will occupy the same winter territory, defending it against any intruding bird (see Alonso et al., these Proceedings). In Gallocanta (Spain) and Camp de Captieux (France) some of these cranes try to spend the winter there unless food supply is not enough for the whole population, in which case they migrate further southwards (Bautista et al. 1995)

Recurrence of migratory route. There are many records of birds migrating every year through a few important localities, as Gallocanta (Spain), both in autumn and spring. But there are also a few records of birds utilizing "secondary" routes. One of these is Swedish bird W-Y-W, born in 1993. The first winter it came to Spain, with its parents and sibling, the family travelled through Villafáfila (NW Spain), and then to the South close to the Portuguese border, a route that only some hundreds of birds still use after major changes in habitat in northern Spain (Alonso & Alonso 1987). This bird has been seen in the same wintering route in 1994 and 1995. On the other hand, there are at least three birds that performed migration through both the SE and the SW routes in consecutive years: they have both contacts in Hungary and in Spain or France (Miikkulainen 1996). It remains to be cleared if these birds changed their migratory route when they paired with a crane that was already using the other route, which could be a reason for the observed change.


Conclusions. Colour banding has proved to be an excellent way to improve our knowledge of some aspects of crane ecology and behaviour, although certain life history parameters require larger sample sizes. Data from individually marked birds will complement the population data already known from studies on unmarked birds, providing interesting information on important aspects that cannot be approached without individual recognition. One example of this is the commented change in migration route, shown by some Finnish individuals.

At first view it seems that crane colour banding is more profitable during winter, if the goal would only be to increase the number of banded birds. It is easier to capture many birds due to their gregarious behaviour, and the captures include both adult and young birds thus decreasing the average mortality compared to the sample of only young birds banded in the breeding areas. The disadvantage of winter marking is that the birds are of unknown origin, unless they are radiotagged and followed to their breeding sites. Banding young cranes in the breeding territories may be perhaps more difficult or, at least, more unpredictable and time consuming, according to our own marking experience in Spain vs. Germany. Nevertheless, we should consider the advantages of banding in the natal areas. Cranes banded that way will be mostly young, and therefore of known age and hatching site, although there are already a few German and Finnish adult birds captured during moulting. Young cranes marked in the breeding territories will probably come back close to their natal areas when they start to breed themselves, thus increasing the possibility of resightings. And in any case they will probably live in areas well controlled during the breeding season by the same ringers.

A point that should receive more attention in the future is the way of recording information on colour banded cranes. Most contacts belong to a few experienced observers, and therefore it should be easy to improve the quality of this information. Colour banded cranes should be carefully observed, whenever possible, to check all familiar relationships, and specially a) if they are paired, and b) if they have any young. The presence of any metal ring, and its position in the bird -tarsus or tibia, left or right- is sometimes crucial to determine doubtful observations. Also the presence of a transmitter attached to the leg or back of the bird is useful in that sense.

Another question to be improved is the way of reporting data on colour banded birds. It is very important that banding data are collected as soon as possible, and anyway before the birds leave the breeding areas or summer gatherings. Every observer of a banded crane should be immediately answered with the banding information. Contact between banders or observers and the coordinator of the data-base should be simultaneosusly reported to persons who act as national coordinators of each country’s crane working groups, and, where possible, through e-mail. Reports including all the contacts should be sent to every country working group at least once per year (at the end of the winter season) and to a central place after banding in the breeding areas (at the end of the summer).

There are some aspects of crane biology that can be easily solved through individual marking and recognition. A further step would be radiotracking of selected individuals throughout Europe.


References

ALONSO, J.A. & J.C. ALONSO. 1987. Invernada de la Grulla Común Grus grus en la Península Ibérica. Pp. 123-136, in J.L.TELLERÍA (ed.) Invernada de Aves en la Península Ibérica. Sociedad Española de Ornitología, Monografía 1.

ALONSO, J.A., J.C. ALONSO, R. MUÑOZ & L.M. BAUTISTA. 1995. Colour-banding and radio-tagging of Common Cranes in Spain. Pp. 125-127, in H. PRANGE, J.C. ALONSO & J.A. ALONSO (eds.) Crane Research and Protection in Europe: Proc. Of the Palaearctic Crane Workshop in Tallin. Estonia. Martin-Luther-Universität, Halle-Wittenberg.

ALONSO, J.C. & J.A. ALONSO. 1990. Proposal of a new coordinated Common Crane (Grus grus) banding program in Europe. Crane Information Letter no. 12. ICF-ECG, 5 pp.

BAUTISTA, L.M., J.C. ALONSO & J.A.ALONSO. 1995. A field test of ideal free distribution in flock-feeding common cranes. J. Anim. Ecol. 64:747-757.

MIIKKULAINEN, A. 1996. Mistä kurjet tulevat? Linnut 2: 12-15.

VAN DER VEN, J. (1995). The European Crane Working Group of the International Foundation, pp. 16-17, in H. PRANGE, J.C. ALONSO & J.A. ALONSO (eds.) Crane Research and Protection in Europe: Proc. Of the Palaearctic Crane Workshop in Tallin. Estonia. Martin-Luther-Universität, Halle-Wittenberg.