Garden Birds. Mike Toms
Читать онлайн книгу.
The small seeds of Niger were originally used to produce a cooking oil by peoples living within eastern Africa, and cultivation probably first occurred in the Ethiopian highlands. The seed was renamed ‘Nyjer’ in the US, in part to clarify its pronunciation and avoid unfortunate associations with a similar-looking slang word, being registered as a trademark of Wild Bird Feeding Industry, a now well-established US company, in 1998. It is sometimes referred to, incorrectly, as ‘thistle’ seed. As a flower, Niger had certainly been introduced to British gardens by 1806, and the species has been known in the wild since 1876. There is a suggestion from national botanical surveys that its occurrence in the wild is increasing, perhaps because of its use in bird food. As a commercial crop, Niger is mainly grown in India, Ethiopia and – to a lesser extent – Myanmar, underlining the global scale of production that ends up on UK garden centre shelves.
Use as a supplementary food for wild birds came rather later, the seed starting as something of a niche ‘conditioning’ product used by cage bird enthusiasts. It was known to be popular with American Goldfinch Spinus tristis and Pine Siskin Spinus pinus in the US in the 1960s, and it was the association with Goldfinches here in the UK that helped its popularity to increase. The seed’s small size leads to it being favoured by fine-billed species like Goldfinch and Siskin, with larger-billed species finding it too delicate to bother with. The small size also requires the use of a special ‘nyjer feeder’, whose small feeding ports prevent the seed from flowing out of the feeder and onto the ground – which is what happens if you inadvertently put the seed into a standard feeder. Initially, it seems that the provision of Niger seed at garden feeding stations encouraged the arrival of Goldfinches, with some participants in the BTO Garden BirdWatch scheme commenting on how they had never had visiting Goldfinches until they started provisioning the seed. Others, however, failed to attract them to Niger, even where it was provided alongside other foods at garden feeding stations. One of the interesting patterns of Niger use by Goldfinches appears to be the move away to sunflower hearts over recent years; this may be linked to the decline in UK Greenfinch populations following the emergence of finch trichomonosis (see Chapter 4) and the release of Goldfinches from competition with this larger and more dominant species. Niger seed may still be an important food for Siskin and Lesser Redpoll Acanthis cabaret, the latter species now being seen more commonly at UK garden feeding stations.
FIG 20. With their fine bill, Siskins are one of the species to have taken to Niger seeds, though they seem to prefer sunflower hearts if these are available and there is little competition from larger species like Greenfinch. (John Harding)
Fat and suet products
Although highly variable in terms of their content, a high-quality fat product may have in excess of 8,500 kcal per kg, something that makes these products particularly attractive for use during the winter months. Fat- and suet-based products come in a diversity of forms, probably the most familiar of which are ‘fat balls’ and square or rectangular blocks. Fat balls almost always used to be sold within plastic mesh netting, something that was occasionally responsible for the death of a feeding bird, either caught by its foot or by its barbed tongue. Although a substantial number of netted fat balls are still sold (and purchased) within the UK market, there has been a welcome move towards un-netted fat balls.
Suet may also be presented in a pelletised form, something that is popular with Starlings, or in or around objects such as plastic sticks or coconut shells – popular with Blue Tits and Great Tits. Suet products often contain additional material, perhaps added to increase the range of species that will take it, to broaden its nutritional composition or to secure a marketing advantage. These include seeds, nuts, berries and insect protein (typically mealworms). Suet products may also contain ash in variable quantities, added in order to bind the material together and to reduce the chances of the product breaking down. Again, the Bird Care Standards Association has a set of rules relating to this type of product, though these are geared more towards the source of the fat, rather than the composition of the product or content of additional material. The standards are as follows:
i) suet should be derived from animals that have received ante- and post-mortem examination by veterinary officers and found to be fit for human consumption;
ii) all suet should be processed at a fully licensed and approved EU or US abattoir, and
iii) any suet products that are blended with peanuts, either in whole or granular form, must use peanuts that contain a nil detectable aflatoxin level.
Live foods
The term ‘live foods’ refers to the provision of insects, typically mealworms and wax worms, which are bred specifically for this and the wider pet food market. These may be provided alive or, more commonly, in a desiccated form. Mealworms are not worms but larvae of darkling beetles belonging to the genus Tenebrio. Within the UK it is the larvae of the Yellow Mealworm Tenebrio molitor that are most commonly used as food for wild and aviary birds, captive reptiles and amphibians. The smaller sized larvae of the Dark Mealworm Tenebrio obscura are sometimes used. As their name suggests, mealworms have a long association with human beings, occurring as pests of grain and other cereal products. Mealworms are fairly easy to rear, both at home and commercially, and a number of companies are now involved in the large-scale farming of these beetles, producing insect protein not just for wild birds and the pets already mentioned but also as a contribution to cat and dog food products and, looking to the future, human foods (Grau et al., 2017).
FIG 21. Mealworms are often very popular with Starlings, Robins and Blackbirds, with individual birds quickly learning to exploit them where they are offered. (John Harding)
Wild birds seem to prefer live mealworms, presumably because they attract attention by their movements, but probably because they are far closer in their composition to wild caught food. Mealworms have a high protein (13–22 per cent) and fat (9–20 per cent) content and are also a source of polyunsaturated fatty acids, essential amino acids and zinc. Perhaps surprisingly, they have a significantly higher nutritional value than either beef or chicken.
Other foods
Bread appears to be a popular food with householders, perhaps because it provides an opportunity for them to direct unwanted crusts or stale slices towards other creatures perceived to be in need of sustenance. Its nutritional value is, in the context of garden birds, unclear. Bread was by far the commonest food provided by householders who responded to a questionnaire survey carried out in Cardiff in the 1980s (Cowie & Hinsley, 1988a), with c. 90 per cent of respondents provisioning bread in both winter and summer. Galbraith et al. (2014) found bread to be the most commonly provisioned food in their study, estimating that the equivalent of more than five million loaves was put out by New Zealand residents annually.
FIG 22. A small number of UK householders put out meat scraps or even whole carcasses for visiting Red Kites. (Jill Pakenham)
Apart from the small number of householders nationally who provide meat for visiting Red Kites Milvus milvus, only a small proportion of the kitchen scraps fed to wild birds here in the UK include meat. The situation is very different in Australia where the provision of meat is fairly typical. This reflects clear differences between the main groups of birds visiting garden feeding stations here in the UK (seed-eating species) and in Australia (omnivorous species, such as Laughing Kookabura Dacelo novaeguineae, Australian Magpie Gymnorhina tibicen and Grey Butcherbird Cracticus torquatus). As we’ll see later in this chapter, the provision of meat has potential implications for wild bird health.
In parts of North America, sugar solution is used to attract and feed hummingbirds. Typically made from one-part cane sugar to four-parts water, the solution is seen as a supplementary food rather than a replacement for the sugars that these tiny birds would normally secure from flowers. While those hummingbirds tested appear to be more strongly influenced by the position of a food source rather than