REPORTS

The Canadian Migration Monitoring Network Ten-Year Report on Monitoring Landbird Population Change Technical Report #1

by Tara L. Crewe, Jon D. McCracken, Philip D. Taylor, Denis Lepage, & Audrey E. Heagy

The Canadian Migration Monitoring Network (CMMN) was formed in 1998 as a cooperative venture among a dozen independent migration monitoring stations, Bird Studies Canada (BSC) and the Canadian Wildlife Service (CWS).  Since then the network has expanded to over 20 stations across Canada that monitor spring and/or fall migration of over 150 species of landbirds, about 80 of which breed in Canada’s boreal and other northern forests and are relatively inaccessible to other monitoring programs such as the Breeding Bird Survey.

Recently BSC published Technical Report #1 on behalf of the network, a report on monitoring landbird population change over the 10 years, 1997-2006.  The full report is available at: http://www.bsc-eoc.org/download/CMMNReport2008.pdf

Data from 11 stations, including Prince Edward Point Bird Observatory (PEPtBO), were used to calculate and assess trends in populations of migrants in spring.  Similar data were used for the fall migration, but PEPtBO was not included in that analysis because it did not start its fall monitoring program until 2001 and consequently did not have the 10 years of data required for analysing fall trends. 

There was a lot of variability in trends detected at different stations and in different regions across Canada.  In general, there were more positive trends detected in Ontario and western regions and more negative trends in the prairie and eastern regions.  Remarkably, PEPtBO spring data showed mainly positive trends, with 49 species increasing and only 6 declining.  Moreover, none of those declines was statistically significant (meaning that they could be attributable to chance rather than a real or consistent trend), while 18 of the increases were significant (meaning that they were probably real and unlikely to be due to chance). 

Of course, as with the stock market, large rates of increase cannot persist indefinitely and we can expect these trends to level off, decline, or even crash in the future.  Ten years is not long enough to detect a truly long-term trend, which is one reason why it is important to keep on monitoring migration following a strict protocol into the future.

Accurate knowledge of population status and trends is fundamental to species conservation, if scarce resources are to be allocated wisely.  The CMMN report draws on data from member stations across Canada and feeds into the big picture conservation planning process.  A recent example of a wider scale assessment is a report entitled: “Population trend status of Ontario’s forest birds”, authored by 18 experts, including representatives of BSC, the Ontario Ministry of Natural Resources, and Environment Canada (CWS); see:  http://www.cif-ifc.org/uploads//Website_Assets/Blancher_et_al.pdf.  It integrates results of several surveys, including CMMN.  The experts who authored this assessment identified several species that exhibited serous declines, but their overall conclusion was that “Trends of most forest birds were stable or positive at the Ontario-wide scale…”   This picture differs from alarming reports of massive declines in migratory songbirds that you may have seen in the media in recent months.  Nevertheless, it is the best scientifically-based assessment of the true situation.  PEPtBO and other CMMN member stations contribute to this knowledge, which is an important building block for conservation.

For more information on CMMN visit: http://www.bsc-eoc.org/volunteer/cmmn   

--- David Hussell

Bird Migration Indices At PEPtBO

Bird Studies Canada gathers statistics on migration from each of the bird observatories that are members of the Canadian Migration Monitoring Network. Bird migration trend graphs are available for each observatory including Prince Edward Point Bird Observatory at:

http://www.bsc-eoc.org/volunteer/cmmn/migmain.jsp

Below is a sample of the graphs that can be viewed for different species of birds banded in the Spring and Fall At PEPtBO.

Spring: + 13.44%/year (1998-2005) *
Fall: + 14.73%/year (2001-2005) n.s.

Legend: Trend values were calculated using Spring or Fall migration data and trends are presented in percent change per year. A negative value indicates a population decline and a positive value a population increase over the period covered at the respective station. Significance level of the trends is indicated by: *** P < 0.005; ** P < 0.01; * P < 0.05; n.s. P > 0.05.