Wednesday, August 14, 2013

2012 data analysis...

I have gotten way behind on this is the synopsis of the 2012 results:
The year 2012 began as a warm and early spring for the Ospreys in the 8 county metro area surrounding Minneapolis and St. Paul, Minnesota. There were no major storms that caused mortalities in the population. Once again there was a significant increase in overall number of occupied nests. There were 90 nests which were occupied* by a pair of adult ospreys, although two of these were determined to be alternate / frustration nests which were occupied by a pair counted at another nest site nearby. As a result, there were 88 nests that were counted as being occupied territories. Eggs were laid in 83 nests (73 in 2011) and 68 of these nests had at least one chick fledge successfully or survive to fledging age (56 in 2011). There were 20 nests which failed (24 in 2011). There are two distinct subcategories under failures; nests where a pair was present but no eggs were laid (five) and nests where eggs were laid but they failed to successfully fledge a single chick (15). Not laying eggs is considered to be a kind of nest failure by other scientists. There were 140 chicks that were known to have fledged successfully or survived to fledging age. There were three chicks which died / disappeared before banding time, and six additional chicks which were known to have died between banding time and fledging, or around fledging time. There were only 57 chicks banded, (using the green / black color band and a silver USFWS band) and 83 remained unbanded (only 41% banded compared to 71% in 2011, and 80% in 2010). This is a significant drop in the number of chicks banded which will affect future research. There were 88 adult Ospreys identified by their bands. Two of these were purple/ lavender bands from Iowa. There were 10 new nests; nine with eggs laid and and one with a pair present but no eggs laid. In addition, there was one nest which was reported for the first time, although it had been active for several years. Nine of those new nests successfully fledged chicks. There were 12 banded Ospreys which were believed to have bred successfully for the first time and their average age was 4.5. (Average age of first successful breeding for males this year was 5.0 years and for females it was 3.0 years).
The overall productivity of occupied nests which were successful rose this year to 77% (70% in 2011, 73% in 2010, 67% in 2009, 65% in 2008). The mean number of young fledged per successful nest was 2.05 (1.94 in 2011). The mean number of young fledged per active nest was 1.68 (1.49 in 2011) and the mean number of young fledged per occupied nest was 1.59 (1.36 in 2011). These numbers reflect a rise in productivity after dropping last year.

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