Here it is....all the 2017 results!
2017 ANNUAL OSPREY PRODUCTION SUMMARY
By Vanessa Greene
The year 2017 was a very successful year for the Ospreys in the eight county metro area surrounding Minneapolis and St.Paul. The first Osprey sightings began to roll in on March 28 and the first osprey that I identified was a returning banded male on his nest on April 1! This year must be characterized once again as a very productive one for the Osprey population in this 34 year study, with the population continuing to grow and expand. There were 132 nests which were occupied* by a pair of adult ospreys. ( 122 occupied territories in 2016. There may be more nests we do not know about.) Two additional nests were frustration nests and therefore not counted as separate territories. Eggs were laid in 122 nests (113 in 2016) and 95 of these nests had at least one chick that was confirmed to have fledged successfully or survived to fledging age (93 in 2015). While the overall number of occupied nests went up, the number of nests where eggs were laid remained fairly static, with an increase in the number of nest failures. We documented 37 nests which failed (30 in 2016). We separate two distinct subcategories under failures; nests where a pair was present but no eggs were laid (10) and nests where eggs were laid but they failed to successfully fledge a single chick (27). (Not laying eggs is considered to be a kind of nest failure by other scientists.)
There were 214 chicks that were known to have fledged successfully or survived to fledging age! (208 in 2016). Most successful nests had two to three chicks. (44 nests with two chicks, 37 nests with three chicks, and 15 nests that only produced a single chick). The mortality rate this year was similar to last year with 19 chicks which were known to have died or disappeared before fledging,(18 last year) with five nests that failed before we were able to see or accurately count chicks. Two adult Ospreys were known to have died and one adult disappeared midseason and was presumed to have died. There were 99 adult Ospreys which were identified by their bands. Two of these were from Iowa. We located 13 new nesting territories, including two nests that were discovered this year, although reports indicated that they had been there for one or more years. Only five of these new nests successfully fledged chicks. Eight banded Ospreys were believed to have bred successfully for the first time and their average age was 4.50 years old. (Average age of first successful breeding for males this year was 5.25 years and for females it was 3.75 years). It is interesting to note that of the 132 occupied territories this year, 74 were on osprey nesting platforms, 20 were on cell or radio towers, 18 were on ballfield lights, 17 were on a power pole or transmission tower, and 3 were on other manmade structures. One nest was built in a dead tree in late 2016, but only a single osprey was seen there sporadically in 2017. Two osprey nests were taken over by geese and one by a Great Horned Owl this year.
The overall productivity of occupied nests which were successful this year was 72%, (76% in 2016, 68% in 2015, 70% in 2014, 67% in 2013, and 77% in 2012). The mean number of young fledged per successful nest was 2.25 (2.24 in 2016, 2.43 in 2015, 1.77 in 2014). The mean number of young fledged per active nest was 1.75 (1.84 in 2016, 1.88 in 2015, 1.41 in 2014) and the mean number of young fledged per occupied nest was 1.62 (1.70 in 2016, 1.65 in 2015, 1.25 in 2014). These numbers reflect a slight decrease in overall productivity per nest, although the number of chicks fledged per successful nests remained similar to last year. The cluster of ten nests which all failed within a small area in 2015 (approx five mile radius), and had seven nests fail in 2016, did better this year, with only four nests failing. Three of those nests failed after hatching was observed, with the timing of failure unknown on the fourth nest. Two nests in that cluster have failed for three years in a row. Weather did have an impact this year, with 6 nests along the northern tier of the study area blown down during large storms in June and July. There were three additional nests where one or more chicks were blown out of the nest in these storms, although at least one chick survived. On one nest the adult female took a beating and was buried in six inches of hail. Two of her chicks were lost, but she somehow managed to protect one chick which survived and fledged. The most interesting behavior documented was a male whose mate disappeared, and presumably died, who took over the care and feeding of three small 3-4 week old chicks as a single parent. He heroically balanced the hunting, feeding and sheltering of these young birds, which all fledged successfully, although one of the chicks was subsequently electrocuted when it landed on a power pole.
The oldest male on record, at 23 years of age, returned and bred successfully, raising two chicks to fledge. This is the oldest bird to breed successfully in this 34 year study. Two additional older males, 18 and 17 years of age, also bred successfully. Our oldest females are quite a bit younger with four 10 year olds that all bred successfully.
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*Successful nests are those that were known to have fledged at least one chick successfully, active nests are those where eggs are laid and occupied nests are those where pairs are present at a nest site for a period of time, regardless of the time of year or whether or not they lay.
Any use or reproduction of this data should be appropriately credited to Vanessa Greene at Twin Cities Metro Osprey Watch.
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