Introduction
The Harlequin duck is a species that is of conservation concern and sensitive to habitat degradation. Their nonbreeding part of the year they spend in nearshore coastal environments. However, their breeding habitat is located in mountainous terrain along fast-flowing streams. If the breeding habitats are changed it could affect the productivity of the harlequin duck.
Background of the Project
It was the aim to identify the traits of breeding streams affecting habitat selection. The two specific questions that were addressed were: do the ducks constitute a significant part of their energy through foraging on breeding streams and is the availability of harlequin duck invertebrate prey being influenced by flow variability and fish abundance? The information gathered will be used to help in the conservation of harlequin ducks.
Methods, Materials and Study Area
The study was conducted within several watersheds including Bridge, Cheakamus and Seton Rivers which all fall under the Bridge-Coastal Restoration Program (BCRP) and several watersheds not listed under the BCRP in the Bridge-Coastal Region including Cayoosh Creek, the Yalakom River, Rutherford Creek, Ryan River and Birkenhead River, to compare with streams that haven’t had any hydroelectric development.
To link harlequin duck distribution with habitat information duck surveys and measurements of the habitat attributes were required. Seven streams of about 5 km in length were selected and surveyed during the pair arrival and laying period. For the brood surveys the number of hens, her ducklings and the age class of the ducklings were recorded. Attributes that were measured at the harlequin duck habitats include invertebrate abundance, flow type, substrate size and composition, number of exposed boulders, stream width, stream depth, flow rate, temperature, pH, slope and vegetation sampling. After all the attributes were sampled, the relationship between those and the harlequin ducks were assessed.
Female ducks were captured, sampled, radio-marked and released again to answer the question of nutrient allocation. The question of food availability was approached as an assessment of variation in invertebrate abundance.
Results
The surveys on habitat associations were successful with seven streams examined in 2003 and six in 2004. There were only six in 2004 because the Rutherford Creek survey was not representing the harlequin duck densities accurately. Out of the 34 captured adult female ducks 22 were on nests and 13 hatched at least one duckling. The research also showed that the relationship between the aquatic insect availability and the flow variability is of a negative correlation. A decrease in flow variability always resulted in an increase in aquatic insect availability.
Discussion
There was no particular habitat attribute that was connected to harlequin duck density. This might show that on every stream different factors might influence the duck density. Female ducks seem to be dependent on access to invertebrate prey in order to produce eggs. Every river that was studied showed variations in aquatic insect availability, a positive association between the insect availability and harlequin density and a negative association between the fish presence and the duck density.
Suggested Action
It’s important to maintain the aquatic insect resources in breeding streams for the harlequin duck. To achieve that the flow variability should be kept low. It is also recommended to keep track of harlequin duck activity in the future.
Conclusion
The research on harlequin duck was conducted to find attributes of breeding streams and examine the selection mechanisms of the variations found. The results showed that distribution and productivity showed that insect food is clearly important to produce eggs. Their distribution is also loosely linked with the aquatic insects density, but fish presence has a negative effect on harlequin duck density.
- Source Dr. Dan Esler, Dr. Ron Ydenberg, Jeanine Bond, Sunny LeBourdais. April 2007. Variation in Harlequin Duck Distribution and Productivity: The Roles of Habitat, Competition, and Nutrient Acquisition. Available at : http://www.env.gov.bc.ca/wildlife/wsi/reports/5074_WSI_5074_RPT_2006.PDF [Accessed 03/2021].