The house sparrow eats sunflower seeds
Deadly sunflower seeds
When bird lovers clean their nest boxes in the fall, they keep discovering one or two mummified or skeletonized tit children in the nesting material. However, these are not yet a cause for serious concern, as such low losses are easily compensated for by nature through the clutch size (great-cabbage and blue tits: up to 12 or 14 eggs). However, there is a problem when the entire brood is dead in the nest.
In one of the last spring a large Schwegler nest box was occupied, as every year - this time, as is usually the case, by a pair of great tits. As is well known, large-scale kittens with a brood chamber area of approx. 14 x 19 cm are supposed to prevent the adult birds from having to land on their offspring with wet plumage or from feeding them only from the entrance hole in the advanced nestling stage, whereby the so-called "nestlings" starve to death. So, as in previous years, I expected a problem-free and successful brood. In April, however, the adult birds suddenly stayed away before the youngsters were expected to leave. At first I assumed that I had missed the time to start breeding, but finally I became curious and checked the nest cavity. Result: nine dead and withered nestlings (Fig. 1), whose large plumage pen sheaths were just about to be torn open.
Half a dozen possible reasons are possible for such a total loss:
- Starvation due to disturbances: This was extremely unlikely here, as great tits within human settlements only react sensitively to strong disturbances, but no such had occurred.
- Starvation due to a lack of insects: There was, however, no pronounced period of bad weather in the period in question.
- Starvation through the death of the parents: possible, but not very likely here as there is no traffic in the immediate vicinity of the property. However, tits are preyed on by cats.
- Poisoning by biocides: was not ruled out, but poison against the "huge aphid plague" was only injected in the neighborhood after the adult birds had stopped (by the way, unnecessary, since the affected bushes are falling out again).
- Death from bacterial disease: quite possible - especially when spoiled birdseed is involved.
- Death due to wrong food: also possible, since neighbors had already maintained their winter feeding into the breeding season in earlier years and the more difficult to digest plant-based diet is still unsuitable for titmice and many other nestlings.
Fortunately, I didn't throw the nest on the compost heap right away, but first photograph it and then examine it. The probable cause of the little tragedy only became visible when I detached the dried up young from the nesting material and discovered 17 (!) Old sunflower seeds between and below them in the upper layer. Apparently, the adult birds had offered the easily accessible sunflower seeds instead of animal protein carriers on which the bird brood is dependent; Their intake was either completely refused, or the young tits actually swallowed some kernels at first, which then either caused a digestive disorder due to their vegetable nature or an intestinal infection due to their bacterial contamination.
But why do adult birds feed seeds instead of insects, spiders, etc.? The answer is certainly related to the fact that the fatty sunflower seeds, which are popular with tits, do not exist in nature during the breeding season, so that the birds were not at all forced to restrict their feeding schedule to animal food for this time in order to protect the young.
In spring, tits collect what is naturally available at this time of year: caterpillars, aphids, spiders, etc .; Large numbers of prey are preferred for reasons of labor economy and determine the currently valid search image - i. H. Key stimuli such as a certain shape, color or movement of the food animal that triggers the capture of prey. If the preferred animal food becomes rarer, some birds can switch to other, particularly frequent prey, i.e. develop a new search pattern.
In the case shown it could have been the case that the great tits appeared to the great tits that the sunflower seeds, which can be easily reached at any time and in any quantity, were a far more abundant and thus more attractive source of food compared to the still available, but perhaps less animal food supply; in their mass they acted as a supernatural trigger for the capture of prey and were consequently "programmed" as a new search image. The fact that this can also break the barrier to food (which is unnatural in spring) can perhaps be explained by the fact that our city tits are very familiar with the sunflower seeds from autumn and winter and that the birds are practically trained for this food, so that they eventually even get into houses. This "civilized" behavior may seem interesting and "cute" to humans, but, as we can see, it is not good for birds.
Bird lovers should draw conclusions from such incidents caused by thoughtlessness and first check
- whether winter feeding is necessary at all: In the mild winters of recent years, it was definitely not;
- Whether the feeding method is correct: Conventional bird feeders all too often turn out to be a deadly source of infection, as feeding is often done at temperatures above zero: With their higher body temperature, birds are better protected against infections than mammals, which have to fend off invading living microorganisms through fever; However, large amounts of food in the same place over and over again (namely in the bird feeder) provoke an unnaturally high parasite load and thus overwhelm the bird organism. Better for grain feeding are simple and cheap but hygienic feed dispensers;
- Whether they really help the needy species or just unilaterally favor the well-known common species: The common, intelligent and adaptable tits in particular could one day displace the rarer species and migratory birds from their ecological niches.
If the bird lover has decided on careful feeding, he should limit this to the real, icy bad weather conditions (but then persevere), at temperatures in the plus range (risk of infection!) Clean the feeding place again and again - and above all: at the latest at the beginning of the Do not offer any more grain feed in the breeding season in March.
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