Various count methods needed to come up with population trends

Nicole Krikun
For the Lakeside Leader

After another busy week of banding 80-100 birds a day at the Observatory, things are starting to get back to normal, meaning catching 20-30 birds a day. We’ve seen and caught a wide variety of migrating warbler species, with the most common being Tennessee warbler. Unlike last week, we have not been catching too many white-throated sparrow.

In light of this busy spell I wanted to write about the importance of both long-term monitoring and using multiple standardized counting methods. Many people looking at the numbers would think, ‘Wow! Birds are doing great and their populations must be going up!’ Although it could be that certain species have had good breeding success this year, there is no way of knowing that by looking at just banding data, because banding success hinges so heavily on the weather.

The reason the LSLBO has been around for so long is that the only way to truly monitor bird populations is to do it every day and every year. That way long-term trends start to emerge and the blips of busy and slow years can be seen as part of a bigger picture. That is also why for all 25 years we have been using four counting methods concurrently, not just doing banding.

On top of the banding we do visual migration counts, once per hour. During a ‘vis-mig’ we count just the birds that are migrating overhead. This gives us an idea of migratory timing of various species and adds perspective to the day – looking at the data we can see if lots of birds were just hanging out and foraging or if it was a day of heavy migration.

The second method is a census. It is a 700-metre transect we slowly walk once every morning. We aim to do it during the busiest portion of the day (around two hours after sunrise) and it lasts half an hour. We are counting every bird we see or hear in the area. The main purpose is to have one person stop everything else and focus on counting. On a busy day it is easy to get caught up extracting birds, banding or interacting with visitors. The census ensures that no matter what, the busiest portion of each day gets thoroughly monitored.

The last count method is incidental observations. As we go about all our other duties we note all the birds we encounter – singing in the forest, flying overhead or swimming on the lake.

So each day we have a ‘daily estimated total’ for each species based on four methods of detection. These totals can be used to come up with population trends.

Cape May warbler

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