Conserve Wildlife Blog

Posts Tagged ‘osprey survey’

Studying the Ridgway’s Osprey of Belize: Part II

Tuesday, March 14th, 2017
Flat calm Caribbean and three young Ridgway’s!

by Ben Wurst, Habitat Program Manager

 

The flat calm beauty of the Caribbean sea.

February 18: Second Survey of nests surrounding Placencia

Our second survey began from Placencia, a small beach resort town on the southern coast of Belize, which is a beautiful place to visit if you’re planning a trip to Belize. It was flat calm that morning, which made for great boating, but it was extremely hot! Life in the tropics was finally setting in… We headed towards the first nest location, which was last surveyed in 2016 by Paul and his team. Paul and Alan have been surveying osprey nests in Belize since 2014, so all known nests have been mapped and surveyed over the past couple years. Through the continued surveys of these nests we should be able to determine if the low productivity of Ridgway’s (around .3-.4 young/active nest) can sustain the population in Belize (the southern most nesting colony of Ridgway’s throughout their range). The work performed as a part of these surveys is critical to their long term survival in Belize. The first nest we visited was very unkept; however a pair was present. This ended up being quite the common sight during this survey.

An unkept nest south of Lark Caye.

An adult female Ridgway’s osprey in flight.

Red mangroves growing in the Caribbean off Placencia.

We then motored to several other small Cayes and surveyed a total of eight nests (only two produced young, photos below). Many were abandoned so it was hard for us to determine their overall fate. Many (good looking) nests Paul thought had failed (once had young or eggs and were lost) since the nests did look like they have been used this year but there were no birds around during our survey. Generally it is hard to determine overall nest success unless you watch a nest throughout the entire nesting season, or find evidence of nest failure when visiting a nest. In New Jersey, I generally can tell when a nest fails or hasn’t by observing the behavior of the adults. If a nest is active (bird present) and it is defending its nest with no young or eggs then it failed. If the nest is active (bird present) and it flies away with no defense of nest/young, then I¬†call that nest active and housekeeping (a term for a bird that starts a nest but does not produce any eggs/young). Lastly, a nest with no birds = not active. Either way – it is very difficult to determine the overall nest success with only one visit/nest/season. If I were to go back to Belize then I would go twice during the nesting season there, which runs from December – March/April (once when birds are incubating and once when they have young). ūüôā

Kept or Unkept nest?? You decide.

While we try to determine the cause of failure to an active nest, we think about potential threats to nesting ospreys. A substantial threat to ospreys in coastal Belize should be no surprise to us in New Jersey. Coastal development was a huge contributor to the decline of ospreys throughout coastal New Jersey. In Belize, there are many resorts on the coastal Cayes and the desire for more. Could this be the beginning of the decline of ospreys in Belize??¬†I hope not, as humans and ospreys can live alongside each other in very close proximity. To develop a Caye, mangroves are first cleared and then sand/coral is dredged onto the island to “fill” it in. Raising the elevation of the island allows buildings to be built and lovely white sand beaches to be manufactured for the enjoyment of humans (and sand flies!). During our survey we saw this in plain view. A nest on Long Coco Caye was still present in a large mangrove tree, however a huge pile of fill dredged into a pile right next to the nest. If this happened during the nesting season then there is no doubt that this nest failed…but, where were the adults?? The more we think about this work and the ospreys of Belize, the more concern we have for their overall safety and stability of their population.

A looming threat to Ridgway’s ospreys is development of coastal Cayes.

While scanning shorelines brown pelicans were a common sight around Placencia.

Kept or Unkept house on a coastal caye? You decide.

Sadly, evidence of humans is all over Belize. Welcome to the anthropocene.

The beauty of a disappearing horizon in coastal Belize. 

A brown pelican thermoregulating atop a red mangrove.

We kept moving along with our survey and ventured outside of the previous survey route to check a small Caye for a nest. Success! We found a nice nest atop a huge almond tree on Moho Caye. Bonus! There were also two large young (5-6 week old young) making this our first productive nest of the day! The island was private and occupied by a friendly caretaker. We talked to him about the ospreys, and he was happy to share the island with them. This just goes to show that ospreys and humans can coexist on the coast of Belize.

Can you spot the nest? 

No need to climb this nest. We wouldn’t be able to anyway. Next week we might bring a small drone to help survey tall nests like this one.

Two young visible along with an adult and loads of plastic bags. ūüôĀ

The guardian. We were glad to see humans and ospreys getting along just fine on Moho Caye and hope to see this in the future too.

We continued to head north and back to Sittee River. Navigating along the edges of the mangrove islands would not have been possible with our experienced captain and his mate, Steve. They really made every survey go extremely smooth. Having boated for the majority of my life, I can attest to the fact that anything can go wrong at any time. You definitely do not want to get into trouble when boating offshore in Belize! There is few other boaters who could offer help, no patrolling of Coast Guard boats, no SeaTow/Boat US, and many islands are totally undeveloped and without freshwater. We are lucky to have had such a great crew to be able to get to us to where we needed to go and then back safely!

Navigating through tiny mangrove islands in search of nesting ospreys!

First mate Steve keeps an eye out while approaching the edge of a Caye.

Our experienced guide and captain Horace.

Guiding Horace through a cut along the edge of a Caye.

Fishing resort.

Siesta time!

Osprey siesta time!

The last nest we surveyed on our way back to Sittee River was one on Channel Caye. This nest was remarkable. It was built in a large dead mangrove and had two visible young. After closer inspection with my camera, we believed that their could be three young, so we decided to climb up and use a mirror to get a view into the nest. Jay T. eagerly climbed the short tree and saw three young. The female took off from the nest as the young played dead, as they do in New Jersey. She was not as upset as our ospreys get (Ridgway’s are less disturbed than NJ’s ospreys and hence less aggressive, IMO) and flew over the nest several times and then perched on a nearby branch, which allowed me to get some great photos of her. We were only by the nest for a couple minutes and quickly departed to let her return to the nest. This was the first time that Paul has ever seen three young in a Ridgway’s nest, so very cool for us to see and document! We surely hoped that all three survived to fledge. Usually by the time they reached the age that they were (around 3-4 weeks), then their chances of surviving were much more likely.

All things considered, there are many concerning threats to ospreys in Belize: nest abandonment, coastal development, plastic marine debris, possible persecution?, and the combined threats from the effects of climate change but we can only hope that from our work we can help improve their chances of surviving.

Stay tuned for Part III where we cover the next two surveys out and back from Turneffe Atoll and Calabash Caye!

Channel Caye female perched on her nest.

Jay peers into the nest.

Female looks on as we exit the area.

The third and elusive nesting!

A cut through to Sittee River.

Sunset on Sittee River.

Studying Ridgway’s Osprey of Belize: Part I

Friday, March 10th, 2017
CWF contributes to conservation of Belizean ospreys

by Ben Wurst, Habitat Program Manager

A male Ridgway’s osprey perched near its nest on a snag off Blue Ground Caye. Photo by Ben Wurst

When I first learned of the work being done by Dr. Paul Spitzer and Alan Poole to study the breeding population of Ridgway’s ospreys (Pandion¬†haliaetus¬†ridgwayi)¬†in Belize, I was instantly captivated. I first met Paul at the Raptor Research Foundation Conference in Cape May last October where he explained the study and the need for partners to assist with this years survey. Some of the aspects that immediately drew my attention was the fact that the estimated size of the population there was around 50 pairs, that those pairs nest exclusively on the coastal cayes (mangrove islands), and that their estimated productivity rate was around .3-.4 young/active nest. The coast of Belize is approximately 170 miles long and protected by barrier reefs and these mangrove islands. (more…)

Osprey surveys completed

Monday, July 30th, 2012
Severe weather may have reduced productivity this year

by Ben Wurst, Habitat Program Manager

Surveys of nesting¬†osprey¬†have ended for 2012. Each year volunteers, state biologist and CWF staff complete nesting surveys of ospreys. These ‚Äúosprey banders‚ÄĚ complete ‚Äúground surveys‚ÄĚ (referred to as ground surveys because they are surveying nests by land/sea, not by helicopter) that cover around 70% of the state population. The surveys are meant to keep tabs on the state population and data collected from the surveys are used to determine the health of the population. Young are also banded for future tracking. Next year a state wide aerial survey will be conducted; the last aerial survey was in 2009 where 486 nesting pairs were found. We won‚Äôt know the total size of the population until then. Nesting success is mixed this year and is highly variable by different regions, mainly because of severe weather.

I never heard of a “derecho” until this summer. According to Wikipedia it is “a widespread, long-lived,¬†straight-line windstorm¬†that is associated with a fast-moving band of¬†severe thunderstorms.” A derecho hit Cumberland, Salem, Atlantic & southern Ocean County in the early morning hours on June 30th, right in the middle of the nesting season for ospreys. Weather plays a significant factor in the success of nesting ospreys. They nest in open areas, which makes them vulnerable to high winds and severe weather, and since they primarily feed on fish, water clarity affects foraging success.

“In¬†South Jersey,¬†Atlantic City Electric¬†reported that 206,000¬†customers lost power from downed trees. Most of the outages were in¬†Atlantic County, which prompted a county-wide state of emergency. Near¬†Atlantic City, a boater died while trying to bring his vessel ashore. Officials believed that lightning struck a 104-year-old church in¬†Longport¬†and caused a fire that damaged the building.¬†An elderly couple was killed when a tree fell on their house. In¬†Vineland, damage was preliminarily estimated at $125¬†million.¬†On July 19th, 2012, President Barack Obama declared three counties in New Jersey (Atlantic, Cumberland, and Salem) federal disaster areas. This assured disaster relief through federal assistance to local and state governments and some non-profit organizations.” (from Wikipedia.com) I also know that two people were killed while sleeping in a tent at Parvin State Park.

Kristin, an intern with CWF puts an osprey nestling back in the nest. © Ben Wurst

At this time most young were between 2-3 weeks old, with some a little older and some younger. All young are very vulnerable to severe weather, especially when wind gusts reach 70-100 mph, they can be easily blown from their nests and if not retrieved quickly could become food for ground predators or washed away with the tide. Winds gusted to 81 mph in Tuckerton, 74 mph in Absecon (Reported by the NJ State Climatologist Dr. David A. Robinson). In three areas that I survey (Absecon, Mullica River, & Little Egg Harbor) many young were either lost or blown from their nests and found dead or live on the marsh. In Absecon 9 of the 22 young produced had been lost or found dead on the marsh as a result of the storm. At a couple other nests to the north a few young were found on the ground shortly after the storm. Off of Great Bay Blvd. many nests that had young before the storm had lost them. One of our volunteers reported that many nests in Ventnor that were previously occupied had no young after the storm.

We can only hope that severe weather like this will not occur during the middle of the osprey nesting season again, but with a warmer climate these might become commonplace in New Jersey. One thing that we might consider is to take a long look at our current design for nesting platforms and look to see if we can make changes to allow for a deeper nest bowl. More of a problem is that some ospreys do not build substantial nests and use little sticks and branches, while others build large nests that are not easily blown away with the wind.

 

  • Subscribe!

    Enter your email address to subscribe to the Conserve Wildlife Blog and receive notifications of new posts by email.

  • Support Conserve Wildlife Foundation

    Support our efforts to protect New Jersey’s rarest animals, restore important habitat, and foster pride in New Jersey’s rich wildlife heritage.

    Join - Donate - Adopt a Species
  • Get Connected

  • Recent Comments