Thirty-seven continuous years of Christmas Bird Counts on the Sunshine Coast (over the years 1979 to 2015) have delivered an enormous amount of data. During that time we can track population increases in some species, declines in others, the first appearance of new species to our area and the near extinction of others. All this is to say that bird populations on the Sunshine Coast are very dynamic, responding to a variety of environmental and human factors.
One well-documented relationship is that between two of our most widely recognizable species, the great blue heron and the bald eagle. Though these are both very large species, it is well-known that bald eagles prey on young herons when they are in the nest. As the eagle population increases, the level of predation on the herons increases, and an increase in eagles would be expected to produce a decline in herons.
The Sunshine Coast data shows exactly this. In the decade of the 1980s, the count found an average of 42 herons and 30 eagles per count. By the present decade, the situation was reversed with only 11 herons per count while the eagles had increased to 115 (and 194 in the current count for 2015). Continentally, bald eagles are still increasing after their brush with pesticides in the 1950s, but one must fear for our local herons in the face of this onslaught.
The statistics also point out some anomalies in certain areas for some species. While the common loon population is steady overall, it has declined quite radically in Sechelt Inlet, along with both red-necked and western grebes, which might indicate some problem with their food resources in the inlet. At the same time, their smaller relative, the horned grebe, has maintained a stable population in both the inlet and elsewhere.
Species that are newly arrived on the Sunshine Coast are thriving, and Anna’s hummingbird (arrived in the 1970s) has a current population of around 300 birds. Eurasian collared dove (first recorded in 2005) is now well-established in suburban-type habitat from Gibsons to Halfmoon Bay.
Full results of the Christmas Bird Count are posted at https://sites.google.com/site/scnaturalhistorysoc/home
To report your sightings or questions, I can be contacted at [email protected] or 604-885-5539. Good birding.
