It is not clear how weather patterns affect the Canberra bird population. There has, as yet, been no systematic analysis of the Garden Bird Survey data to see if there are any relationships between rainfall or temperature and the bird abundance. of garden birds. However, readers might find useful some information about the variations in weather over the survey period. The rainfall and temperature information is based on data from the weather bureau at Canberra Airport.
Rainfall
Since the survey year, which coincides with the annual bird breeding cycle, runs from July to June, the annual average rainfall for each financial year is shown in the graph below. On the whole, the rainfall throughout the period showed expected variability around an annual average of about 595 mm, although the long-term average is slightly higher at 617 mm.
The average rainfall over the last ten years of the survey (98-99 to 07-08) was just over 550 mm, compared with an average of 650 mm for the previous ten years.
Eight of the 27 years of the survey were in drought, including 1981-82, 82-83, 90-91, 97-98, 02-03 (the driest year of the survey period), 03-04, 04-05, 06-07 and 07-08. There were only two particularly wet years, 1983-84 and 1988-89 (nearly 1000 mm). In 1983-84, most of the rain fell in May 1983 with late spring and summer being particularly wet, with almost 200 mm falling in January 1984.
The graph Monthly Average Rainfall shows that over the years, Canberra gets less rain in winter, and more in late spring and summer.
Temperature
An inland city, Canberra experiences a considerable range of temperature, although its altitude prevents temperatures from climbing too high in the summer. The average summer maximum
temperatures are in the range 25?30 degrees Celsius, winter maximums being around 12?15 degrees, and with winter minimums hovering around 0 degrees Celsius.
To give some idea of how temperatures have varied over the 27-year survey period, three graphs are provided. The first is the annual average temperatures over the years. This shows which
years were warmer or cooler on average.
2006-07 was the warmest year, with an average daily maximum temperature of 22 degrees Celsius. This was more than three degrees warmer than 1992, a comparatively cool year. The average
daily maximum temperatures in January 1981 and 2007 were around 31.5 degrees Celsius where by comparison, January in 2000 was about 7 degrees cooler. The comparison of the maximum
temperatures throughout 1983-84 and 2006-07 are in the graph below.
1983-84 was the coldest year, with an average daily minimum temperature of 5.9?degrees Celsius. This was two degrees cooler than 2006-07, a comparatively mild year. June 1984 was quite
cold, with daily average minimum temperatures at 2.7?degrees Celsius.
