The Birds at my Table

by Darryl Jones

  Provisionally? Yes, of course. As we would all be aware, there are some situations when withdrawing food supplies would certainly be hazardous and, indeed, unethical. Prolonged periods of extreme weather such as blizzards, storms, or severe drought all present serious challenges for birds seeking sustenance. Similarly, the increasingly frequent instances of certain species apparently overwintering instead of migrating—perhaps because of the reliable availability of feeders—may represent genuine reliance. In these cases, it is quite likely that the birds would simply die without our providing food.

  Some have argued that providing food in these situations is perpetuat-ing an artificial regime, that we are interfering with the processes of natural selection. Others, while acknowledging that to be possible, nonetheless counter with the welfare argument: that we bear clear responsibility for the well-being of the birds that have chosen to utilize the resources we have provided.40 And yet others suggest . . . a range of philosophical positions, which we will return to later in this journey. For now, we can accept that for most of the time, our supplies are just a part of the birds’ overall diet, although there are also certain times when external conditions are such that we really do need to keep feeding.

  Are Feeder Items Used as Food for Nestlings?

  This discussion returns us to the important issue of parent birds utilizing inappropriate feeder items as nestling food. As we have seen, most observations seem to indicate that breeding birds typically do not use feeders as a significant source of food for their young. Although some studies of tits did find that some seed was used in this way, invertebrate foods—such as caterpillars, spiders, aphids—were always the most common items.41 A more specific concern, however, is the risk of choking on a large item such as a peanut, an entirely valid worry. Thankfully, this has been rarely observed; nonetheless, it does happen. Richard Cowie and Shelley Hinsley seem to have been among the first to report dead Great Tit nestlings (only three) with large pieces of peanut stuck in their tiny throats,42 a story repeated endlessly ever since. Other researchers have related similar stories in other species—including Florida Scrub Jays—but always as rare and atypical events.43 These incidents really do appear to be the exceptions that prove the “seed is not used very often as baby food” rule. Where it did occur, there were strong suspicions that the particular birds involved were inexperienced or, more commonly, simply desperate. After all, we now know that large numbers of all tit nestlings in suburban environments starve before they leave the nest, almost certainly because of a lack of suitable insect food.44 Feeding seeds to chicks may actually be evidence of the general lack of suitable insect food in the local area and of the grim reality for the parents valiantly attempting to keep their brood going. Feeding seeds to chicks may be a symptom of poor conditions but is unlikely to be the main cause of the breeding failures. Significantly, Cowie and Hinsley and others have found no relationship between the amount of seed in the diet of nestlings and their likelihood of survival, another reassuring result.

  Does Feeding Change Bird Populations and Communities?

  Finally, we need to consider perhaps the grandest of all the claims associated with feeding: that the provision of feeders actually changes the numbers of birds being fed. This is crucial because such an effect underlines some very important propositions: that feeding aids the conservation of declining species, and that feeding may increase the abundance of pest, invasive, or just unwelcome species. How much do we know about these important issues?

  The global popularity of wild bird feeding means, among other things, that a huge amount of food is offered—and accepted—by birds throughout the world every day. Various figures have already been cited to emphasize the volume of this provisioning—for instance, 60,000 tons of bird seed is distributed annually in the UK, or enough to support 71 million birds (twice the estimated population size of the top ten feeder species!).45 Another metric sometimes mentioned is the number of feeding devices being presented. One study from Michigan found a density of 8.5 feeders per hectare in urban areas, 2.6 for suburban, and 2.8 feeders for rural areas. This averages out at about 600 bird feeders per square kilometer (or twenty-three per square mile) for this state.46 Similarly, in the UK one national survey found the density of feeders to vary from about fifty to over 1000 per square kilometer (twenty to 390 per square mile) with an average of 925.47 It probably doesn’t mean much—given that we don’t have similar data for almost anywhere else—but one location within the city of Sheffield in England was found to have the highest density of bird feeders in world: 1208 per square kilometer (460 per square mile).48

  Beyond the simple fact that these are apparently large numbers, and that they indicate something quantitative about the popularity of bird feeding in these different places, we also need to acknowledge that these figures represent a truly massive intervention by humans in the lives of birds. If food is a fundamental influence on the lives of the birds around us, we are almost certainly changing things in some way. How much do we really know about these possible changes?

  The answer to that question is “frustratingly little!” It is surprising, but despite the enormous numbers of people actively engaged in bird feeding at their homes, the growing scientific interest in urban environments (as indicated by the emergence of the field of “urban ecology”), and the scale of the bird food industry itself, our knowledge of the effects of wild bird feeding is quite meager. Let me clarify this claim. We do know a lot about the preferences many species have for the different types of food, both commercial and otherwise, and much research has been conducted into the nutritional and dietary balances and suitability of many seed mixes and bird food products. The results of these detailed research programs mean that—with a moderate level of care—we can be reassured that the items we buy to be offered as food are likely to attract the species we wish to attract and that the food value of these products is suitable.

  These are research topics of primary interest to the massive bird-food industry: the suppliers, the seed companies and the increasingly discerning consumer/feeders. If the birds don’t eat some fancy new mix, there are plenty of other products to choose from. This is the normal dynamic of the commercial marketplace and has led to the proliferation of products and gadgets we see today. What is still missing, however, is a clear understanding of just what happens when birds are attracted to our feeders. While we may enjoy seeing lots of chickadees or tits, what does it mean for the birds themselves?

  There has been, thankfully, one very recent and important study that does provide at least some light here. Led by Travis Wilcoxen (mentioned above) the study assessed a wide range of physical features of the community of birds using their experimental feeders in woodland sites in Illinois and compared them to the features of birds without access to feeders.49 The feeders supplied exactly the sort of general seed selection typical of the area and were replenished three times per week for two years. Over 1600 birds of 11 species were carefully captured and examined in one of the most comprehensive and relevant studies so far conducted. What they found was genuinely reassuring: in general, the fed birds scored significantly better on numerous parameters than the unfed birds: increased antioxidants (an indicator of health), reduced physiological stress levels, more rapid feather growth, and generally better body condition. Overall, this was the first decent evidence suggesting that feeding might actually be good for the bird’s health.

  But of course, there was a down side too. The feeder birds were also much more likely to show signs of several diseases (especially avian pox)—exactly as expected from a process that brings lots of birds of different species together—although there was also some evidence that sick birds with access to feeders were able to recover more rapidly. So, some good news mixed with some (not unexpected) bad. More studies like this are desperately needed.

  Is More Less?

  The density of feeders, a measure of the anthropogenic feeding resource available, provides one measure of how the distributio
n of bird food may be influencing the numbers and diversity of species of birds across the landscape. Because the number of feeders per area varies from none to lots, it is possible to assess whether spatial changes in food availability relates to differences in bird numbers. Two British studies lead by Rich Fuller, conducted at both national and local levels, provide clear evidence that feeder density strongly predicts bird abundance: the higher the density of feeders, the more birds.50 But lots of food did not mean more species, just more individuals. The second study found much the same pattern, though with additional details of certain species. In Sheffield, at least, the density of House Sparrows, Blackbirds, and Starlings related directly to food supply. Somewhat surprisingly, this relationship did not hold for either Great or Blue Tits, despite them being feeder stalwarts. The same pattern was found in Michigan, with more feeders leading to more birds in general but not more species.51

  This general pattern of an increase in food supply leading to a larger abundance of birds—more individuals—but without attracting additional species is a familiar picture to ecologists studying birds in cities. Compared to forest or woodland, urban environments across the globe exhibit the same pattern of having far greater numbers of birds, particularly pigeons and corvids, but distinctly lower diversity of species.52 Although there are many possible reasons for this pattern, including fewer predators, warmer temperatures, and the tendency for some species to cope better with the presence of humans, by far the greatest influence seems to be the foraging opportunities provided by cities. In their review of how birds living in cities have been affected, Dan Chamberlain and his colleagues concluded that “food availability was paramount,” with human-provided foods being the primary source.53 Rich Fuller and his colleagues went so far as titling one paper: “Garden bird feeding predicts the structure of urban avian assemblages.”54 In other words, all those feeders are definitely having a fundamental influence on the composition of bird life in our cities.

  Of course, simply having more birds may be a worthy goal in itself. At the level of one’s own backyard, attracting a colorful congregation of favored species by providing feeders may be exactly the intention. It is important to appreciate, however, that a reliable and plentiful source of food represents an artificial concentration of a high-quality resource that will certainly attract many birds. Ignoring for the moment the other possible implications of bringing lots of birds, and species, into close contact at a feeder (increased aggression, attraction of predators, exchange of disease, for example), simply seeing lots of birds does not necessarily mean a larger local population of that species.

  This was certainly the case in Auckland. Josie Galbraith’s innovative work on bird feeding in the suburbs of New Zealand’s largest city has already been mentioned above in the context of understanding what happens to the birds when feeding stops. While this earlier study found that the birds simply dissipated to preseason levels, her more recent research investigated how the initiation of feeding influences the overall community of birds.55 This work is especially important because it appears to be the first to investigate the feeder effect in places where feeding had not occurred previously. By comparing the diversity and abundance of birds before feeding started to what occurred 18 months later, Josie was able to demonstrate significant increases in the numbers of most of the already common species but virtually no change in the number of species. What was of most interest, however, was which species prospered or and which did not. In Auckland, feeding greatly increased the numbers of House Sparrows, Spotted Doves, and Starlings, all species introduced to New Zealand. House Sparrows, already the most abundant bird prior to feeding, more than doubled its numbers with feeding. Although numerous native species were present, feeding affected only one, the Grey Warbler, and this was to decrease their numbers.

  Josie interpreted the changes to mean that the type of foods offered has fundamental importance. Her experimental feeding regime replicated what most New Zealand feeders were offering—bread and small seeds— and this almost certainly favored the foreign species, famously granivores or eat-anything generalists. The local natives, such as White-eyes (Silvereyes), Tuis, and Grey Warblers, on the other hand, were nectarivores or insectivores; those bird tables would have been of little interest. For a place like New Zealand, desperately trying to maintain its unique wildlife in the face of an ongoing insurgence of foreign invaders, these are sobering though illuminating findings. Time for some feeding advice?

  Special Seeds

  Sometimes, however, there is a very clear influence of a particular food type on the abundance of certain birds. Of course, this was what happened when black sunflower seeds first began to be provided widely: the seed was spectacularly popular with a wide variety of species, with birds flocking to feeders everywhere. This was probably the single biggest influence associated with bird feeding, but was so generalized and widespread it was impossible to document. By the time researchers began to take an interest, the phenomenon had stabilized. We simply cannot know just what the bird community would look like without black sunflowers because they are effectively already everywhere.

  It is, however, possible to know more about the likely impact of more recent seed introductions. The clearest example would probably be that of the small black high-oil seed known as nyger (or nyjer or niger, and sometimes “thistle”). Although this seed was known to be highly attractive to American Goldfinches and Pine Siskins in North America as far back as the 1960s, it was the remarkable reaction of Goldfinches to what was a new offering in Britain that was quickly noticed.56 Goldfinches are one of the European species that traditionally were seen only in gardens when supplies of their natural diet—the seeds of dandelions, ragworts and groundsels, for example—were at a low ebb. The arrival of nyger changed all that virtually overnight, according to Chris Whittles, founder of CJ Wildbird in the UK. “Nyger was a niche product mainly used by cage bird enthusiasts as a ‘conditioner’ prior to breeding. The wild goldies, but also Lesser Redpolls, Siskins, and Dunnocks to some extent, also seem to really go for it just before the breeding season. But the way that the Goldfinches took to this one seed type as soon [from the early 1990s in the UK] as it was available was phenomenal.” The BTO’s Garden BirdWatch data for Goldfinches matches this observation: over a 12-year period, Goldfinch sightings went from 23% to 60% of all gardens.57 That’s a lot of birds. Of course, these reports were from gardens and not the countryside, but it does seem that this is one species that is actually increasing in abundance nationally in Britain. “It’s hard to prove, of course,” cautions Kate Risely from BTO. “But the growth in Goldfinch numbers does correlate fairly well with the advent of nyger.”

  So it is possible that this may be a case where effectively the entire national population of a particular species really has benefited from a particular feeder food. Another example is almost certainly going to be a surprise, unless, of course, you live in the city of Reading, a little west of London. Here a most unexpected bird is being actively encouraged to visit local gardens by the provision of an unusual type of bird food: meat. Large amounts of pork, beef, and lamb, but primarily chicken, are being placed in gardens with the explicit aim of attracting a large bird of prey, the Red Kite. Now many feeders have an uneasy relationship with their local birds of prey, particularly species such as Sharp-shinned Hawks or Sparrowhawks that are often found in urban environments. Indeed, considerable efforts are made to minimize the risk to smaller birds visiting garden feeders from avian predators. Yet according to recent research by Melanie Orros and Mark Fellowes, almost all of the people feeding Red Kites in Reading also fed smaller species.58 “They did worry about their smaller garden birds,” Mel Orros told me when I visited her, Red Kites wheeling over the nearby M4 motorway to London. “But the wonder of seeing such a majestic and wild creature swooping down into your own back yard is really a special experience, especially in a typical English town.” “Of course,” she adds, “they also believe that they are assisting in the
recovery of a previously extinct species!”

  Reading happens to be relatively close to the Chiltern Hills, where Red Kites were originally reintroduced in 1989, having been absent from Britain for centuries. The remarkable story of the return of a large raptor to the countryside—largely through the use of supplementary provisioning of vast amounts of meat—is described in detail in Chapter 8 as a particularly successful example of feeding for conservation. For our present purpose, however, this background provides a valuable context to what may seem an incongruous activity. Many local people were well aware of the rein-troduction program and were pleased to know that a great conservation story was unfolding nearby. But when Red Kites started appearing within the city itself, the possibility of being able to see Red Kites close by in one’s own garden was certainly worth a try. Mel showed me astonishing photos of these fearsome-looking birds of prey swooping down to pluck bits of meat carefully arranged on the back lawn. I couldn’t help wondering about whether the Blue Tits would still visit the feeder in the background.

  Benefiting the Wrong Species

  While we all have favorite species, including those that turn up only occasionally, there are also birds we would much rather not attract. This may be because these species are unwilling to share the feeder, are particularly messy or noisy, or simply because we don’t like them for no particularly obvious reason. Sometimes these species may be overtly aggressive and their presence may prevent any other birds from visiting; there are plenty of stories of people who have given up feeding altogether because they attracted only species generally disapproved of: various corvids, grackles, Starlings, and feral pigeons all come to mind. More common are situations where feeders attract large numbers of certain species whose presence prevents other species from visiting, or invasive species such as Common Mynas, exotic pigeons, and (in places where they are not native) sparrows. In the main cities in New Zealand, for example, the most common feeder birds by far are House Sparrows and Blackbirds, both introduced to that country and doing very well indeed.59 As has been known for some time, some of the “cheap” seed mixes are notorious for attracting a range of unpopular species, possibly because part of the success of these birds in urban environments has been their willingness to try a wide range of foods. Again, there can be little doubt that the abundance of these familiar “street” birds has been at least partially due the presence of so many feeders.