Factors Influencing Bird Sightings

Ground-nesting ovenbirds are vulnerable to several threats in small fragments.

Ground-nesting ovenbirds are vulnerable to several threats in small fragments

Let’s say you’ve “ naturalized” your yard or part of it with the hope that wildlife will be drawn to it. Will the critters come? Only time and the experience of several or more seasons  of observation will tell. Most likely species of some kind will appear such as butterflies or other insects that you haven’t seen before. And surely unexpected plants will appear.  But what about birds?

My partially converted yard (all 1/2 acre of it) in central Florida is a definite stopping off place for a number of migratory bird species,  which probably I would not otherwise see. Included here are Swainson’s Thrushes and Rose-breasted Grosbeaks which feed on the native Callicarpa americana (beautyberry) shrubs I planted. But a  host of  factors interact at different spatial scales  to determine which species  might appear in, for example, my yard:

1. Sub-continental scale- Birds, of course, are known for their migratory habits. About 75% of North America’s species, ranging from swans to hummingbirds, migrate to some extent. Many of these species tend to follow predictable migratory paths or flyways which may or may not pass over a local area. Besides the obvious, that species with western ranges migrate south without  going through eastern states, and vice versa, many species are unevenly distributed within their migratory area. For example, among warblers passing through Florida, Blackpoll Warblers are much commoner and more widely distributed in spring than in the autumn within Florida, while Bay-breasted Warblers are much commoner in the autumn than in the spring.  Many species tend to concentrate along the coasts, sometimes the Gulf (Hooded Warbler) or the Atlantic (Connecticut Warbler), while a few (e.g. American Redstart) are more numerous inland.

2. Regional location- In central Florida, 18 miles from the Gulf of Mexico is close enough to the coast to see wide-ranging species associated with salt water but not more sedentary ones. Thus, Double-crested Cormorants, Royal Terns, and several gull species can be seen overhead, but not other larids (gulls, terns), plovers (except killdeers) and sandpipers, sea ducks, etc.

3. Local landscape- there are small cypress swamps, and lakes within a mile and oak-pine forests within 5 miles. These provide shelter, feeding and nesting habitat that may augment local bird populations. Lake edges and swamps bring in egrets, ibis, limpkins and others which fly over or occasionally visit the yard. Osprey, and less often Bald Eagles  visibly soar over near-by lakes .

Sadly, the area being described is undergoing rapid conversion of remaining undeveloped lands to asphalt and concrete at a pace that seems to be  Florida’s speciality. Will this unfortunate trend destroy wildlife habitat and squeeze out species intolerant of man’s heavy hand, and has it already done so? Most likely, yes on both counts, although some species like mockingbirds year-round and Palm Warblers in the winter appear undeterred by this development.

4.  Local surroundings- My place is in what has become “old suburbs” though urban expansion from the south. In my and in adjacent yards, there are large oaks, both laurel (Quercus laurifolia) and live (Q. virginiana), laurel cherry (Prunus caroliniana) and red maple (Acer rubrum) plus exotic species such as Chinese Elm (Ulmus parvifolia) and camphor (Cinnamomum camphora). The oaks and maple provide nesting for a few species like Cardinals and Red-bellied Woodpeckers and foraging opportunities for many species. Robins and waxwings seek out camphor and cherry fruits which ripen in the winter! It turns out that our Chinese elms are better hosts for “Spanish moss”, than the oaks, to the apparent satisfaction of Parula Warblers that are here all year.

5. Within the yard are plant species attractive to birds in different seasons. e.g., as mentioned above, Callicarpa  which provides berries used by fall migrants, and native coral honeysuckle (Lonicera sempervirens ) which attracts hummingbirds and frugivores. Also water-for drinking and bathing, in my case provided in aquatic plant containers. Yes we have the customary bird bath but it is not optimally situated nor kept replenished sufficiently to meet birds’ needs. In addition, the containers have enough water (and algae, etc) to support frogs, insects (e.g., dragon- and damselflies) and smaller aquatic life. To prevent mosquitoes, Gambusia (mosquitofish) are maintained in some containers. Another factor operating locally is the general adversity of small yards to ground-dwelling birds such as ovenbirds and towhees.

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