Around 50 of these birds are reported to roost in Stuttgart in winter. But reliable population counts from the last couple of years are lacking. The history of these birds is that in 1984 one escapee showed up around the Stuttgart Wilhelmina Zoo, interested in the captive parrots there. The zookeepers fed the bird and it survived trough the winter. In early summer of 1985 the zookeepers released another bird so the escapee could have a companion. In 1986 the first breeding commenced and the present 50 or so birds all stem from them. Which is a remarkable population growth (Franz).
There is some confusion on the exact subspecies to be found in Stuttgart. All the birds we encountered were well within the characteristics of the Amazona oratrix oratrix. Confusion might have arisen from immature birds that only have limited amounts of Yellow on their heads. Clearly we haven not seen all birds and some Amazona oratrix belizensis might be present or have been part of the founding population. Non of the photographed birds shows the greyish orbital ring which is telling for belizensis.
Although most authors locate the amazons in Rosensteinpark and Wilhelmina Zoo, we found the greatest density at the adjacent Unterer Schlossgarten close to the Abstellbahnhof. We could locate 5 nests there within the stretch of Platanus trees that parallel the rail tracks. The nests are fairly close together, 4 of them found within 50 meters from each other and the 5th within 100 meters. Suggesting semi-colonial breeding. Two, more isolated nest, were found in Rosensteinpark itself within hearing distance of the colony.
One of the Rosensteinpark nests was special as there was a mixed couple attending it. We found one Blue-fronted Amazon (Amazona aestiva xanthopteryx) paired with a Yellow-headed Amazon. The blue fronted was apparently an escapee wearing a ring. The numbers 239 could be distinguished on the ring. Later we identified one possible hybrid offspring of this pair in our photos. This mixed species pair was the only observed pair not breeding in Platanus trees. They choose a Tilia vulgaris or Lime tree. Would be interesting to hear from anyone that knows if Blue-fronted x Yellow-headed Amazon hybrids are fertile.
One evening we visited the roost at the Eisenbahnstrasse. As expected not many birds showed up at this time of year preferring to sleep on the nests, brooding eggs or young. We only counted 8 birds. The birds that did come were remarkably quite in comparison with the Amazon roosts in San Diego and Temple City. Not a sound was uttered which is a big contrast to their daytime activities, which were always paired with their relentless calls.
Their daily activities did follow the usual Amazon schedule: first hours directly after sunrise and the last couple of hours before sundown. The breeding colony was very active. This was largely due to one, we believe younger, pair that had not decided on a definitive nest site. It picked fights with other couples in the colony. The older (more yellow on the head in both sexes) pairs were decided on nests and concentrated on brooding eggs. Vocalizing battles with this younger couple were swiftly decided in favour of the older pairs who would co-ordinately chase the challengers and set them straight if need be. In contrast these vocal battles, where one pair duets against another, could take hours when two younger, undecided pairs engaged.
Yellow-headed Amazons are well known for their aggressiveness around the start of the breeding season. Although there were some tense moments in the colony no physical fights between the parrots were observed.
The inexperienced pair did however get physical with an unfortunate stock dove (Columba oenas), with fatal consequences.
We observed this Amazon pair pick fights and inspecting potential nest sites all morning. The plentiful stock doves use similar cavities in the Platanus trees. The pair and the stock dove had been sitting at opposite ends of a suitable cavity that the Amazons inspected often, with no sign of aggression. The amazons however flew to other cavities as well. After inspecting an alternative nest the amazons returned to the former site. Which the stock dove had apparently entered. It all happened very fast and we did not get the skirmishing on camera. Next thing we observe is the stock dove plummeting towards the ground beneath the tree where the two amazons sat site by site at the nest cavity. The stock dove took a few moments to die. Exhibiting the symptoms of a broken neck. We subsequently found bite wounds to its neck. The Amazon pair, which we now call Bonnie and Clyde, apparently dragged the unfortunate creature out by the neck.
Parrots are known to kill in protection and in takeovers of nests. Nest cavities are a scarce commodity in their native forests and this nest territory aggression has a long evolutionary history. We have observed our macaws fight Nile geese over the control of nest cavities. But never did we observe casualties.
Bonnie and Clyde went on to inspect other nests and did encounter pigeons on them. Apparently not that interested in these nests the pigeons were able to chase Bonnie away after allowing her a quick peek.
The Yellow-headed Amazon is an endangered species. It suffers much from habitat los. But the population suffers most from the many thousands that are taken from the wild and smuggled abroad to feed the international pet trade. The domestic trade in Mexico is also extensive. Many of the poached birds die before getting to their final destination. Tragically many of these birds are subsequently given up to parrot sanctuaries both in Europe and the US. The noise they produce and their tendency to bite are often too much for an inexperienced owner to handle.
After all this it is not without irony that these birds have managed to start and maintain a population in such an alien environment, as a German city must be.
Once again an endangered parrot species finds sanctuary in a city. No reports of poaching have reached us, although this population could yield a generous annual income. As always city people have day jobs, are general unaware of the wildlife that surrounds them and will think twice risking their lives and limbs climbing up a 20 meter ladder to wrestle with angry parrot parents while trying to rob their nests. It's hard to get away with cutting down centuries old trees in busy city parks to get to a parrots' nest (although it has been done).
People from the countryside are otherwise inclined especially in the rural areas where parrots are native. Cutting down trees might be compared to a national sport and poaching parrots one of the few ways of making cash.
Because of these threats the Stuttgart Amazons should be considered potential future reintroduction stock. In conjunction with the European parrot sanctuaries the Wilhelmina Zoo, who started this population, could be instrumental in improving the genetic base of this population. The more capable birds in these sanctuaries could be rehabilitated from the zoo and join the flock. In a generation or two the Stuttgart flock could then help build City Parrot populations in native Mexico. Where they would be comparatively save from poaching and sustain the remarkable population growth urban parrot populations are renowned for.
Many of the Stuttgart parrots show signs of geophagy on their bills. Traces of dirt left on the bill. We also directly observed this behaviour. A pair of Yellow-headed Amazons ate the dirt that had collected in a moist pit in a Platanus tree. With the present controversy on this important part of a parrots diet insight might be gained on the exact role of geophagy in a parrots diet by studying the Stuttgarts' parrots.
Another intriguing behaviour is the extraction of the marrow of young leaves of elderberry (Sambucus). The caloric value is probably minimal arguing for a case of self-medication. Although other explanations are possible elderberry has many medicinal purposes. If it is the case parrot natural behavioural studies might lead to the discovery of more plants with medicinal uses.
The Stuttgart Amazon parrots were a delight to observe. One thing we found especially appealing is that once we discovered the breeding colony we started to identify single animals and their relationships. The varying amounts of yellow on their heads make these birds individually recognisable. Combined with the relative ease with which the colony is observed makes them an ideal research population. A wealth of knowledge could be gained from studying the natural behaviour of these birds.