Tag: museum of natural history

two swifts looking out from their nesting area

More than a Dodo3 Comments

A Swift Return to Summer

By Chris Jarvis, Education Officer

Amidst reports during the last week of Swifts being sighted feeding over the nearby Farmoor reservoir, Museum staff have kept their eyes to the skies eagerly waiting to be the first to spot our resident birds returning to their breeding site in the nest boxes of our tower. A wet and windy weekend caused by a deep depression over Britain meant little opportunity to feed on their diet of small flies and other invertebrates that make up the aerial plankton they relish, and which normally drifts unseen above our heads in large numbers on still summer days.  The high winds would certainly also have made any attempt to land, for the first time in a whole year since they left their nest boxes and for the first time ever for those just reaching maturity, extremely precarious, and so it seems our Swifts headed farther afield, possibly back to continental Europe, for a few days to await better conditions.

swifts flying around the museum tower against a cloudy sky
Swifts flying around the Museum tower by Mark Garrett

However, this morning, the 5th of May and right on cue, we were treated to the first two Swifts performing a low, high speed fly-by of the tower. Having flown around 14,000 miles in the last year from the Museum’s tower to their winter feeding grounds in southern Africa and back again, the Swifts have arrived on exactly the day of their average time of arrival over the last couple of decades.  We know this because the Swifts in the tower are part of an ongoing study which is the longest running study of any bird colony in the world, started by David Lack in 1947, our Keeper of the Swifts, George Candelin still climbs the spiral stone stairs and ladders each week under red lights to carefully and quietly monitor each nest box throughout the breeding season an count and ring each chick noting down all sorts of other data as he does so from wind speeds to egg rejections, weights and even altercations between birds in boxes over rights to nest sites.  Whilst you can’t be involved in the weighing and ringing of the birds, we do offer the next best way of getting involved; our nest box webcams, which you can find on our ‘Swifts in the Tower’ page, allow you to watch all the action live as it happens from the arrival of the adults to the final fledging as the next generation takes wing for the first time. Hidden microphones will also allow you to hear as screaming parties bang their wings against the nest box covers in order to ascertain if they are occupied and the keening noises of begging chicks!  George’s stats and comments will also be downloaded to the Swift’s Diary each week enabling you to get a full picture of what’s happening across the colony’s 147 nest boxes as the season progresses.

Swifts have markedly declined in numbers over the last few decades, and their breeding season is one of the few times anyone has to measure population changes and you can get involved, too.  Check out if there is a Swift City project near you like Oxford Swift City @oxford_swift or @EdinburghSwifts to get directly involved in monitoring projects or just record your Swift sightings to the RSPB at their Swift Mapper site. All your observations give us a really good idea of how these enigmatic summer visitors are doing!

Update-in the half hour it has taken to write this blog post: the number of Swift’s flying around the tower is up to 5-and they’re screaming!

Summer is here!

More than a Dodo2 Comments

Excavating amber

First amber excavation in the El Soplao outcrop, Cantabria, N Spain in 2008. Credit IGME-UB.

By Dr Ricardo Perez-De-La Fuente, Research Fellow

Amber, or fossilised plant resin, is a unique material to learn about the history of life on Earth. Its incredible preservation and ability to capture life “in action” are well known thanks to the Jurassic Park saga, but fewer people know where amber is found, what it looks like in the field, and how it is gathered.

Cretaceous amber, about 130 to 70 million years old, is the oldest amber that provides abundant fossils, specifically insects and spiders. Ecosystems drastically changed during this period due to global greenhouse conditions and the diversification of flowering plants, among other factors. Amber from that time has been discovered in Lebanon, Spain, France, Myanmar, eastern United States, Canada, and northern Russia.

My research team and I carry out regular amber excavations in northern Spain, working in teams of six to ten people. The outcrops that we excavate are often located next to roads and highways because amber is typically uncovered during roadworks. Excavations take place during the summer or fall to try and minimise the risk of rain, and we usually embark on one field trip each year.

The goal is to recover as much amber as possible – usually a few kilograms – from the muddy and sandy sediments. These materials were transported downstream tens of million of years ago by heavy rain and river swellings from the forests where the resin was produced, before being finally deposited in near-shore areas.

Manual extraction of amber. Credit IGME-UB
Manual extraction of amber in the El Soplao outcrop, Cantabria, northern Spain in 2008. Credit: IGME/UB.

I find amber excavations quite romantic. In the field, amber has a dull appearance that makes it difficult to distinguish from rocks or woody remains. This is due to an opaque crust resulting from oxidation in the sediments and other processes.

This outer layer makes detecting potential fossils inside the amber highly unlikely while the excavation is ongoing. So, in the field we just gather as many amber pieces as possible, and hope for the best.

Only when amber is polished – or shows broken surfaces – does its distinct yellowish to reddish shine emerge, and any possible fossils within become evident. Some ambers are highly fossiliferous, while others are very poor in fossils.

Amber can be gathered by hand using regular tools such as hammers. However, the most efficient method to extract amber from soft sediments is with concrete mixers! This rather unsophisticated piece of equipment provides the best way to recover medium quantities of amber in the field.

We charge water and amber-bearing sediments into the mixer, and after stirring for a while amber floats to the top because it is less dense than muddy water. Then, the surface of the water containing the amber is poured into sieves, which separates even the tiniest pieces.

Amber pieces recovered in a sieve after washing
Amber pieces recovered in a sieve after having been “washed” from their sediment. First amber excavation in the La Manjoya outcrop, Asturias, northern Spain in 2017.

After fieldwork, many hours will be spent looking for fossils within the amber and preparing them. Gathering raw amber is just the first part of a process in unearthing the secrets held within – fragments of encapsulated time.

Top image: First amber excavation in the El Soplao outcrop, Cantabria, N Spain in 2008. Credit: IGME/UB.