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Ian Stewart

Migration is a fascinating aspect of animal biology. Each spring and fall, millions of birds, mammals and insects fly thousands of miles to get to either their breeding or wintering grounds. Migration can be challenging to follow however, as many of these animals migrate at night and travel quickly. There are several methods scientists use to track migration but a new collaborative method has recently emerged: the Motus system.

The Bucktoe Motus tower

The Motus system is an international network of automated towers which detect any animal fitted with a special small tag within a 15km range (‘Motus’ = Latin for ‘movement’). Since each tag emits a unique signal it is possible to track the movement of individual animals as they pass by one of more towers. The great majority of animals fitted with tags are birds but tags have also been placed on bats and large insects like dragonflies or even butterflies! The Motus network allows scientists to collect data on tagged animals to help them find out how variables like weather and the animal’s age, sex, and physical condition affect the timing and speed of their movements. It also aids conservation efforts by identifying key areas where animals stop to feed and rest during migration which can then be protected.

There are over 200 towers spread across the world, most of which are in North America (see the map on the Motus homepage www.motus.org). In the summer of 2017 a team of dedicated field biologists erected a line of towers all the way across Pennsylvania. The towers are so close together that their detection ranges overlap, meaning that they would pick up every tagged animal that migrates north or south anywhere in the entire state!

Distribution of Motus towers across PA and DE

Thanks to generous funding from the Starrett Foundation and the Pennsylvania Department of Conservation and Natural Resources via the Willistown Conservation Trust, a Motus tower was erected at Bucktoe Creek Preserve near Kennett Square in August 2017 as part of this line and has been recording 24/7 ever since! In the fall of 2017 it detected 7 thrushes, 3 warblers, a woodcock and a bat, all presumably heading south for the winter. In the spring of 2018 it detected a thrush and 4 shorebirds, all likely heading north to breed.

Another remarkable feature of the Motus system is that much of the data is open-access and can be viewed by anyone with the Internet. To see what animals are being detected follow these 4 simple steps.

1. Visit the homepage at www.motus.org then scroll down to see a map of the world with a yellow dot representing each tower.

2. Zoom in to find the tower you’re interested in (e.g. Bucktoe Creek) and click the dot. A box will then open telling you the name of the tower and its location plus the contact details of the organization overseeing it. The bottom row gives the number of tags detected by that tower (if there have been any) with ‘table/timeline’ in parentheses next to it.

3. Click on ‘table’ and a new page will open with several columns including the date each tag was detected plus the ID# of that tag (in blue text) and the species it was placed on.

4. Click on the ID# to reveal the date and place where the animal was tagged, and then if you want to explore further, either click on ‘table’ in the bottom row to see a list of towers at which that bird was detected, or ‘timeline’ to see what time the animal passed by the tower and how long it stayed. My own favorite is to click on ‘map’ to show the route the animal took!

Every year more Motus towers are erected throughout North America and they are also starting to spread across other continents. The number of tagged animals is also steadily increasing and every time one is detected it adds to our understanding of animal migration. Watch this space for updates from the Bucktoe tower!

By Ian Stewart

For over 4 decades Delaware Nature Society has been providing homes for birds in the form of wooden nest boxes. We currently have over 200 boxes spread across the properties we own or help manage and every year literally hundreds of young Bluebirds, Tree Swallows, Chickadees and House Wrens fledge from our boxes. In some years we are pleasantly surprised to open one of our boxes and find nests of unexpected species like Carolina Wrens, Tufted Titmice or even White-breasted Nuthatches.

Adult male Purple Martin at gourd

This year one of our long-standing volunteers, Steve Cottrell, attempted to attract a new and charismatic species to our nesting list – the Purple Martin! The Purple Martin is the largest swallow in North America, and gets its name because the adult males have purplish-blue feathers over their whole body. Females are purple above but pale below and sub-adult males (those hatched the previous summer) look like females but have purple blotches on their breast. Martins are long-distance migrants that spend the winter way down in the Amazon Basin, especially Brazil, and many people across the country eagerly await the return of these shimmering gems each spring.

Purple Martins are widely but patchily distributed across the eastern United States because they tend to only nest in colonies of artificial houses and won’t be found where these aren’t present. Martins are quite fickle however, and many people erect brand-new houses in what seems like an ideal place (away from trees and preferably near a good source of insects) and yet never attract any martins. Steve was one of those unlucky people and had tried to attract martins to his yard for 5 years without success.

Steve in front of the Ashland Purple Martin tower

He therefore decided to donate his three Purple Martin towers to us! Each of these towers is equipped with a dozen plastic nesting gourds which are made of white so they stay cool inside and a large screw cap on the side for easy checking. Steve erected one tower at Ashland Nature Center and two at Bucktoe Creek Preserve near Kennett Square, Pennsylvania.

Steve lowers the martin gourds to check contents

Steve and Delaware Nature Society staff members anxiously watched the towers throughout spring and were thrilled to spot martins perched at all three towers in late April! We had an even bigger thrill last week when we found at least one Purple Martin nest with eggs at both of the Bucktoe towers and then just today, a nest with 5 eggs at Ashland! This is the first confirmed breeding by Purple Martins at both Ashland and Bucktoe!

Steve checking the Ashland gourds for nests

Eggs found in the Ashland tower

We will be checking the gourds each week to follow these nesting attempts and see if we are lucky enough to get any more. Later in the summer we hope to band any nestlings produced to try and track their movements during migration and winter and also see if any return to our sites in 2019!

We will also be banding nestling Purple Martins at their long-established colony at DNS’s Abbott’s Mill site in Milford on June 30th and at Flint Woods Preserve in Centerville on July 11th so check out those programs if you want to see these beautiful birds up close.

And if you want to try to attract them to your own property, check out Wild Birds Unlimited in Hockessin and the Purple Martin Conservation Association’s website at https://www.purplemartin.org/. Be lucky!

By Kristen Travers

April and May showers may bring flowers but for our streams rain can also bring problems. Recent rains have resulted in our streams resembling unappetizing chocolate milk more than the clear clean water that we want to see.

Before many people lived in the Delaware region, most of our area was covered in forests, wetlands and marshes. When it rained most of the rain water would slowly infiltrate (soak) into the ground and into the groundwater. Today our landscape also includes homes, businesses, and shopping centers. Rain water can’t soak through impervious surfaces such as roads, building and parking lots but instead runs over these surfaces picking up contaminants and sediment and quickly flowing into our waterways.

Data on our local streams clearly shows how as stream flow increases during storm events, so does the cloudiness of the water as measured by turbidity – a measure of the relative amount of suspended particles such as sediment.

Bare soil, dirt exposed from poor construction and farming practices, and stream bank erosion caused by excessive flows cause increased turbidity. Muddy water harms aquatic life, smothers habitat, and increases water temperatures. It can also be a health concern to drinking water sources and recreational uses since harmful microbes found in animal and human waste bind to soil particles.

Providing opportunities for rain water to slowly infiltrate into the ground can keep pollutants and sediment out of our waters while reducing flooding

Rainwater and soil are assets that should be kept in place:

  • Soak it Up: Add native shrubs, trees or perennial plants who’s deep root systems help to break-up soil and promote infiltration, while also holding the soil in place.
  • Cover it Up: Cover bare soil with mulch and more importantly plants!
  • Prevent It: Minimize chemical use on lawns and in our houses, don’t mow right up to the creek, and pick up after your pets.

Thank you to the volunteers involved with the Delaware Nature Society Stream Watch, White Clay Wild & Scenic program, and Nature Conservancy Stream Stewards for their dedication to monitoring and improving the health of our waters.

 

By Kristen Travers

Snowy, icy days can make us thankful for the salt applied to make our roads safer yet road salt has a less safe side for our waterways. When ice and snow melt, the salt goes with it, washing into our streams and groundwater. As with people, streams are healthier on a low-salt diet as high salt concentrations can harm plants, fish and other wildlife. And considering how easily salt can corrode our cars it’s not surprising that high salt levels can impact infrastructure including roads and pipes and municipal and industrial processes that use water from streams.
Salt visible on a roadway

To understand the potential issues with road salt, volunteers and staff from the White Clay Wild and Scenic Program, Delaware Nature Society, and the Nature Conservancy have been monitoring our local streams.

On Mill Creek – a tributary of White Clay Creek – in Hockessin, average conductivity (a measure related to the level of dissolved salts) have shown large spikes over the winter season as melting snow and rain have flushed salt into streams and groundwater.
Graph showing average conductivity

These high peaks – which correspond to winter rain & snow events – are not seen during other times of the year.

Larger spikes were also documented on Hurricane Run, a small stream near Talleyville DE, which flows into the Brandywine Creek. The high spikes are probably correlated to snow melt and rain washing salt off the many roads and parking areas around Concord Pike.

Chloride concentrations over 250 ppm can make water taste salty and levels over 800 ppm are harmful to aquatic life.

While there are no easy solutions to the road salt quandary, municipalities and homeowners can consider smart salting practices including:

  • Consider using sand and alternate products for sidewalks and driveways
  • Reposition downspouts and snow piles so that water and melting snow isn’t refreezing on paved surfaces
  • Keep salt piles covered
  • Proper calibration of salting equipment and training programs for salt applicators

To learn more and get involved with other projects contact:

www.delnature.org

www.nature.org/ourinitiatives/regions/northamerica/unitedstates/delaware/index.htm

whiteclay.org/