Friday, March 20, 2015

2014 Summary...

Here is the 2014 summary...
The 2014 Osprey season in the eight county metro area surrounding Minneapolis and St Paul began late after a very long, cold winter. We did receive reports of Ospreys as early as March 1, but we were not able to confirm any Osprey sightings until April 6. Some eggs were laid unusually late and there were chicks which did not fledge until late August. The adult male stayed and cared for these late chicks for a full month, not departing until early October. The overall number of known occupied nests dropped this year. (There may be more nests we do not know about.) There were 12 nests which were occupied last year but were empty this year. Four pairs from those nests moved to a new nests and six additional single birds moved to a new nest with a new partner. There were 101 nests which were occupied* by a pair of adult ospreys. One additional nest had only a single osprey observed. Eggs were laid in 89 nests (94 in 2013) and 71 of these nests had at least one chick that was confirmed to have fledged successfully or survived to fledging age (70 in 2013). There were 30 nests which failed (33 in 2013). There are two distinct subcategories under failures; nests where a pair was present but no eggs were laid (12) and nests where eggs were laid but they failed to successfully fledge a single chick (18). (Not laying eggs is considered to be a kind of nest failure.) There were three additional nests, discovered late in the season, where it was not known if eggs were laid or not, but no chicks were ever observed. There were 126 chicks that were known to have fledged successfully or survived to fledging age. There was a high mortality rate in 2014 with 33 additional chicks which were known to have died or disappeared before fledging. Three adults also died or disappeared midseason; two from one nest and another at a nest very near. There were 94 adult Ospreys identified by their bands. Two of these were from Iowa, one was from southern Ontario. There were only 9 new nesting territories that we know of. Only three of these new nests successfully fledged chicks. There were 9 banded Ospreys which were believed to have bred successfully for the first time and their average age was 4.10 years old. (Average age of first successful breeding for males this year was 4.29 years and for females it was 3.67 years).
The overall productivity of occupied nests which were successful this year was 70%, (67% in 2013, 77% in 2012, 70% in 2011, 73% in 2010). The mean number of young fledged per successful nest was 1.77 (2.08 in 2013). The mean number of young fledged per active nest was 1.41 (1.55 in 2013) and the mean number of young fledged per occupied nest was 1.25 (1.39 in 2013). These numbers reflect a drop in productivity per nest, largely due to the high mortality rate. The causes for the mortalities are not clear. A few losses can be attributed to storms, but many cannot. Swarming of black flies were observed at some bandings and one chick that was being viewed on a web cam, seemed to have jumped to its death to escape the flies.
Vanessa Greene
(Any use of this data should have its source appropriately acknowledged.)

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