Sunday, March 30, 2014


The year 2013 began as a very late and snowy spring for the Ospreys in
the 8 county metro area surrounding Minneapolis and St. Paul,
Minnesota. With so many lakes still frozen, many Ospreys did not
return to their nests as early as they did in 2012. We did receive
reports of Ospreys as early as March 20, but many did not arrive at
their nest sites until mid to late April. Once again there was a
significant increase in overall number of occupied nests. There were
105 nests which were occupied by a pair of adult ospreys. In
addition, there were three nests where ospreys were only seen briefly,
and two nests where only a single osprey was observed. Eggs were laid
in 94 nests (83 in 2012) and 70 of these nests had at least one chick
that was confirmed to have fledged successfully or survived to
fledging age (68 in 2012). There were two additional nests reported
that were not confirmed as successful. The mortality rate was high, 
with 33 nests that failed (20 in 2012). There are two distinct subcategories 
under failures; nests where a pair was present but no eggs were laid (9) and
nests where eggs were laid but they failed to successfully fledge a
single chick (22). There were two additional  nests, discovered late
in the season, where it was not known if eggs were laid or not, but
no chicks were observed.  Not laying eggs is considered to be a kind
of nest failure by other scientists. There were 146 chicks that were
known to have fledged successfully or survived to fledging age. (there
were two additional chicks reported that could not be confirmed).
There were two chicks which died / disappeared before banding time,
and 15 additional chicks which were known to have died between banding
time and fledging, or around fledging time.  Two additional adults
died or disappeared midseason.  There were 98 adult Ospreys identified by 
their bands. Three of these were from Iowa, one was from southern Ontario 
and one was from Wisconsin.
There were 22 new nesting territories (this does NOT count nesting
territories that have been active in the past, were unoccupied for one or
more years and then reoccupied) ; 15 where eggs were laid. One of
these nests was reported for the first time, although it had been
active for several years. Twelve of these new nests successfully
fledged chicks.  There were 15 banded Ospreys which were believed to
have bred successfully for the first time and their average age was 4
years old. (Average age of first successful breeding for males this
year was 4.1 years and for females it was 3.8 years).
The overall productivity of occupied nests which were successful
dropped this year to 67%  (77% in 2012, 70% in 2011, 73% in 2010, 67%
in 2009). The mean number of young fledged per successful nest was
2.08 (2.05 in 2012). The mean number of young fledged per active nest
was 1.55 (1.68 in 2012) and the mean number of young fledged per
occupied nest was 1.39 (1.59 in 2012).  These numbers reflect a drop
in overall productivity, with a slight rise in the number of chicks
per successful nest. 

I will post a new entry soon with an explanation of terms, and thoughts on research 

Friday, March 21, 2014

March 21, 2014

I am still doing final counts on my tabulations from 2013 to be SURE the numbers are accurate...meanwhile, as we wait for the birds, I know many of you are interested in the stories of specific ospreys. I find myself thinking of four ospreys in particular. One is the male who will be the oldest this year. Mr 79 who has nested for many years at the Arboretum (which now has a cam on it) will be 22 years old if he survived another migration. He has a history of being a late return to his territory. His mates have often beat him back and engaged in some extra pair copulation and he has had to chase off some other males. Last year he got a new, young female, but their nest failed. I am anxious to see if he makes it back. The second oldest male would be Mr B4. He would be 21 this year. He has been a reliable male, with several mates but this would be his 13th season with his mate, if they both survived. He is the last of the hacked birds from the reintroduction. He was translocated from northern MN and released at the Cedar lake hack site. He returned to MN when he was two years old and spent that summer hanging around the Medicine Lake hack site, where I was the hack site attendant. He then nested on Mooney lake in Wayzata in 1996, moved to a nest on the lights at Wayzata West Middle School in 2001, and then moved to a nest on private property on Robinsons Bay and has been there since 2004. The oldest female will be 20 this year and is nesting on the Lake Minnetonka Regional Park Cell tower where she has been since 2000. The other female that I am anxious to see is the female on the Edina nest who had some eye issues last year. I hope she could see well enough to care for herself and to survive another migration. She was hacked out in Iowa and will be 12 years old this year. Those of us who have been watching these birds for years grow very fond of our winged friends!

PS Hacking is a falconers is a technique for slow release of non flighted birds. This population of ospreys is the result of reintroduction efforts. Nestling ospreys were collected in northern MN and translocated to several hack sites in the metro area. A hack box is a large box(6ft x 6ft) on scaffolding with hardware cloth on the outside to protect these non flighted chicks from predation and yet to allow them to see their new home territory. I was one of the hack site attendants who fed the chicks small pieces of fish twice a day until they developed enough to be ready for flight. We had several different methods for releasing them when they were ready. They flew and learned to fish while we continued to provide food for them until they naturally dispersed. They imprint on the area where they learned to fly and return when they are old enough to breed. So B4 is a bird who went thru that process and returned to nest and has produced 38 chicks.

Monday, March 10, 2014

Well osprey it is 2014 and we are preparing for another osprey season. I am working hard on last years report, making charts, tabulating results, checking and rechecking all my data to be sure it is accurate. Many of you may have seen the post on the MOUnet about an osprey seen in Sherburne NWR a few days ago! That is a very early return in any year, but especially this year with all the snow and frozen lakes. Surprise, surprise. I wonder what other surprises are in store  for us! We always need volunteers to help monitor all these nests (105) so email us you want to get more involved! More posts are coming about research methods and the 2013 numbers.