Osprey Diary 21st July

We are still receiving lots of good osprey questions via email to :  ospreys@swt.org.uk. What’s yours?

Q: I keep seeing movement of small birds on the osprey nest – what are they and why are they there?

A: There have been lots of small visitors to the osprey’s nest- blue tits, great tits, and even a young Great Spotted Woodpecker this morning. These birds are often seen on and around the nest tree but have gotten a bit bolder now no ospreys are in full time residence. They are being attracted by the tiny insects inhabiting the nest lining and structure- these are living off the scraps of old fish, bird feaces and feather dander.

 Q: When will “Lady” leave on migration this year?

A: This is difficult to answer- she is on the loch today sitting on flat top tree this morning so she is still around. Last time she failed to breed in 2011 she stayed around until   7th August which is just a wee bit earlier to leave on autumn migration than usual. What she will do this season is anyone’s guess right now.

Q: As the ospreys haven’t raised any young this year will they return to the nest next year?

A: Yes, if they both survive the winter and migration, they will come back to the same nest and try again. Their loyalty to a successful nest site is very strong and one year of failure won’t be enough to put them off.

 Q: Do ospreys breed every year? How many chicks do they usually produce over a lifetime?

A: Yes ospreys generally breed every year, starting at between 3 and 5 years old and continuing as long as they survive-average life expectancy is estimated to be between 10-15 years in most osprey populations.

On average most pairs have 2 chicks per year with good years of three chicks balancing out poor years of only one or even none. From an ospreys perspective therefore, one year with producing chicks isn’t a huge deal in terms of lifelong productivity but when you have a species trying to recover from local extinction it is a lost opportunity.

All this just goes to highlight how remarkable the achievement of our female osprey is- 50 chicks have survived to fledging from her nest so far!

Photo by Mark Westgarth

Photo by Mark Westgarth

Ranger Emma

Posted in Diary 2014 |

A Fishy Story 17th July

 Here is a great story from locals George and Sheila McLuskey from Perthshire, who have kindly given permission for us to share their great story with you all.

“George and Sheila McLuskey got a surprise when they came home one evening recently. George got out of the car and, looking up, saw the gutter was smashed.

The broken gutter. as you can from the picture, even had fresh blood where something had hit the roof.

The damaged gutter

Sheila also got out, looked down and saw a large trout lying on the mat at the back door. George is a keen fisherman but they were puzzled to work out how the fish had arrived. Was it a flying fish? They are not known in Scotland! Then they spotted claw marks on the body. Had a cat got it? No cat could have hauled that fish around, certainly not up to the roof!

The only thing it could have been was an osprey, probably from nearby Loch of the Lowes, where they breed. Carting its fish supper back to feed its family, the bird must have found it too heavy so had dropped it on their house as it flew overhead. Just as well no one came out of the door at the time!”

fish on mat

It is not unusual for ospreys to accidentally drop their catches on route, and the usually don’t pick them up again as they dislike being grounded where they are vulnerable.  I also have had farmers ask my why they keep finding fish tails in their fields far from rivers- these had been dropped by the birds as they are inedible and they don’t want them on the nest attracting flies.

Ranger Emma

Posted in Diary 2014 |

Wildlife Diary 15th July

What a warm summer it is turning out to be here in Perthshire, with properly sunny days suiting us and the wildlife alike! That is of course, except for Saturday, the one day we needed sunshine as we hosted a free workshop and guided walk by the British Dragonfly Society’s Scottish officer Danielle, to learn to identify damselflies and dragonflies! Despite the drizzle we saw dozens and dozens of Common Blue Damselflies and learnt a lot more about where to look for them and how to get involved in their conservation- we have lots of information here if you are interested, just ask us next time you are in the VC!

A Speckled wood butterfly

On a similar note, we’ve had an exciting siting of a rare butterfly here this week- a Speckled wood. This butterfly is expanding its range in Scotland as the climate warms and is turning up in new places each year. Butterfly Conservation are looking for reports and sightings- ask us for a submission postcard or check out their website.

Elsewhere in the reserve we have been surveying for Beaver activity and vegetation impact – the resident family on the loch consisting of two adults and their two kits from last year, have been showing a remarkable preference for Rowan saplings recently around the loch. Interestingly initial results how that more than 80% of the small trees felled by the Beavers over the last 18months have already coppiced (i.e. regrown from the stumps).

Lastly, on the lochs we sadly we did have to catch a mute swan today on Craiglush with a badly broken wing ( thanks to the visitors at Craiglush House for reporting this to us) which was unfortunately not fixable and was euthanized to relieve its suffering by the SSPCA inspector who kindly came to assist. The swan seems to have had a bad collision with something- possibly during a fight or with a solid object. Sadly this leaves its mate alone on the loch without a spouse as swans are monogamous - hopefully next spring it might find a new young mate.

Ranger Emma

Posted in Diary 2014 |

Whats Happening with our Ospreys? 11th July

Both our resident ospreys are still in the area although their visits to the nest are getting less frequent.   The male delivered a fish this morning to his mate just before 9am and both birds showed normal behaviour towards each other. Both have been spending time on perches around the Loch and in particular flat topped tree, where the male was seen delivering a stick yesterday- is he beginning to build a frustration eerie? If you visit us you will need some patience to see our birds but they are still about.

Q: The ospreys seem to have been mating again – why?

A: Yes there have been quite a few mating attempts between our pair- mostly the female has given him the brush off and we don’t think any have been successful. In all the footage we have recorded, there have been no attempts where the female’s tail height and the male’s position have been right for successful fertilization. This is obviously the strong hormonal urge in the male to procreate, but the mating won’t be successful if females reproductive cycle isn’t right in terms of timing.

 Q: Will they still lay more eggs this year?

A: No, it is highly unlikely the female could lay a second clutch at this very late stage. Ospreys do sometimes second clutch if their eggs are lost or destroyed very early in the season but not this late in the year. The birds know that if they laid now, the chicks would not have time to mature enough before the autumn migration window to survive.

Q: Is Lady moulting- she seems darker? Is it still the same female on the nest?

 A: Yes, it’s still our old lady, but yes she has had a makeover! She has almost completed her annual moulting and has new darker feathers growing in all over. She seems very dark by comparison to April when her old tatty feathers were very faded but these have now been replaced.

Q: Will you be doing any satellite tracking of other chicks this year?

A: In the absence of Loch of the Lowes osprey chicks this year we had looked into the possibility of satellite tagged another young osprey from an SWT reserve in Angus. This is the same place Blue YD came from- this year the parents are doing well and have two chicks. However, the timings on this nest and the availability of the expert team to do the tagging unfortunately haven’t worked out. There is only a very small window of opportunity when the chicks are around 42 days old when they are the right size and temperament to ring and tag. If they are too old there is a chance they will try to fledge as the climber approaches instead of ‘playing dead’ and this introduces a risk of injury etc. We feel the bird’s welfare must always be paramount so have decided to not attempt this nest this year.

This sadly means a fallow winter season this year for our exciting satellite tagging project, but we have high hopes that the transmitter will be used here next year and continue to reveal more migration secrets of ospreys.

Ranger Emma

Posted in Diary 2014 |

Osprey Egg News 8th July

Our ever helpful friend at the National Museum of Scotland, Bob McGowan , has taken a professional look at our osprey eggs which were removed from the nest after the birds gave up incubating unsuccessfully for 74 days.

Our initial observations were that one egg ( the rounder one) was much smaller than average and only weighed   39.1gms, whereas the oddly elongated one was a more normal weight of 52.9gms. By contrast last years unhatched eggs weighed 46.9, 49.8 and 50.6gms.

Both eggs were intact and showed no sign of structural damage, ruling out the crow attack as the cause of hatching failure. The eggs were candled- a light process similar to xray- and it was immediately obvious that there were no embryos inside either egg. In other words, there were no partly developed chicks inside , and the couple of incidents when the male osprey left them alone and cold for a period during later incubation can also be ruled out as the cause of hatching failure.

The eggs were then carefully blown- the rather smelly contents removed and examined closely. One egg ( the smaller round one) was completely ‘blank’, and had not been fertilized at all and had begun to dry out. Unfertilized eggs are common in nature and we have had instances of this before in this nest.

The second, longer heavier egg had a few spots of blood among the fluid, which means it was fertilized initially but development probably stopped at a few days, very early in the incubation period. We cannot say why this happened , but again this is not unusual in eggs when an embryo is not viable or conditions are not right.

So the conclusion to all this is that the cause of our breeding failure is a fertility issue, rather that any fault during incubation. By far the most likely cause of this is our female ospreys advanced age , though there is a slight possibility that it might be the male who has the fertility issue ( he could be firing blanks so to speak) or that we have a case in in breeding depression ( a term scientists use to describe the low fertility of a pair of animals who are too closely related and therefore not a good genetic combination and don’t produce many viable offspring) .

We cannot blame either bird for the lack of breeding success this year, but we have to accept that this pairs fertility is now been low for 3 years and may always be so.

Lastly, what was fascinating as ever was to see our eggs in the context of the reference collection in the museum with ospreys eggs from all over the UK- there was a fascinating wide variation in colour and size of course.  What was truly heart-breaking though was to see at least two full clutches of osprey eggs that had been robbed by human egg thieves from nests not 5 miles from Loch of the Lowes in the 1990′s. These had ended up in the collection after the thieves had been caught and prosecuted and their collections confiscated- how sad that these may well have been the potential offspring of some of our birds descendants, cruelly denied the chance ever to hatch. What a sad reminder of why we still need to do osprey nest protection watch and how close the threats have come in the past to our precious birds.

Ranger Emma

 

Posted in Diary 2014 |

Summer Wonders

Your ranger has welcomed three new residential volunteers to her team recently – welcome aboard Rebecca, Charlotte and Christos ! These stalwarts will be working full time with Emma this summer on a packed programme of wildlife and botanical surveying on the Perthshire reserves, and a lot of habitat management such as removing invasive weeds.

This week alone we’ve been Bracken cutting at Keltneyburn meadow, Himalayan balsam pulling at Ballinluig Island and butterfly surveying at Tomdachoille island on the river Tummel. Here’s a couple of photos of the wonderful species we sighted amongst the vast array of native wildflowers on the meadows, such as Ringlets, Green veined Whites, Common Blues and Dark Green Fritillarys, Small Peal Bordered Fritillarys and Northern Brown Argus:

Small Bordered Fritillary Butterfly

common-blue

NBA

Why not get out and about this weekend and take a look at what Butterflies are around your local patch? All records and useful- send them to www.butterfly-conservation.org

Ranger Emma

 

 

Posted in Diary 2014 |