American tanagers’ colours and songs, new study


This video is called Colombia Tanagers [various species].

From Wildlife Extra:

Study dispels Darwin’s theory to prove birds can have it all

Despite popular belief birds can have a brilliant plumage, a virtuosic singing chirp and an intricate dance routine say scientists.

The author of a new study, Nick Mason, from the the Cornell Lab of Ornithology in New York state, challenged the long-held notion, first proposed by Charles Darwin, that for a bird species to excel in one area it must give up its edge in another.

For example, male northern cardinals are a dazzling scarlet, but sing a fairly simple whistle, whereas the dull brown House Wren sings one of the most complicated songs in nature.

Mason and his colleagues tested the theory by examining a very large family of songbirds from Central and South America, the tanagers.

This group consists of 371 species and included some of the most spectacularly colourful birds in the world such as the paradise tanager as well as the more drab birds, such the black-bellied seedeater. The group also includes both accomplished and weak songsters alike.

“If there were going to be any group of birds at all that would show this trade-off, the tanagers would be a very good candidate, because there’s all this variation in song and plumage complexity,” Mason said.

“But when we dived into it and did some rigorous statistics, it turns out that there is no overall trend. Tanagers can be drab and plain-sounding, or colourful and musical, or or anything in between.”

It’s still possible that trade-offs take place at the level of genus, Mason said, or that they influence species relatively fleetingly as evolutionary pressures appear and disappear.

But as a broad effect on an entire family of birds, a voice–plumage trade off doesn’t seem to exist. One possibility is that the resources needed to develop fancy plumage are different from the ones required for complex songs, freeing tanagers to invest in both forms of showiness simultaneously.

United States songbirds migrate with the wind, new study


This video from Canada says about itself:

Indigo bunting, Blackburnian warbler, stop on migration at my bird feeder

14 May 2013

My first sighting of Indigo bunting, Blackburnian Warbler, photos and video on their way North, Woodslee, Ontario.

From Wildlife Extra:

US songbirds are found to migrate with the wind

Millions of tiny songbirds, many weighing less than an ounce, migrate thousands of miles from North America to Central and South America each year. How they do it has been somewhat of a mystery, but now scientists have discovered how far they take advantage of prevailing wind patterns to save calories.

“Most of what we’ve known about migration routes comes from ducks and geese,” said Frank La Sorte, a Cornell Lab of Ornithology research associate and lead author of the paper in the Journal of Biogeography. “But terrestrial birds are much smaller and they aren’t reliant on the same kinds of habitats. There really isn’t a narrow migration path for them, and they aren’t necessarily in the same place in spring and fall.”

The findings from this study are important as they may help refine ideas about how and where to plan for conservation along migratory pathways.

“All these species migrate at night, at high altitudes, where we can’t see them,” La Sorte said. “But when the sun comes up in the morning they have to find somewhere to land. So any new knowledge about where they’re travelling is valuable to conservation planners.”

For years US scientists assumed songbirds followed the same well-defined “flyways” that ducks, geese, and shorebirds used to travel up and down the continent. There is one known wildfowl flyway along each coast, one up the Mississippi River valley, and one in the centre of the country. Those flyways were marked out from studies which compiled data from recoveries of birds with leg rings and records kept by hunters, but those methods don’t work for small songbirds that migrate at night.

The new work solved this problem with a fresh approach using crowd-sourced data submitted to the Cornell Lab’s eBird project between 2004 and 2011. The researchers analysed thousands of people’s sightings to develop, for each of 93 species, an aggregate picture of where a species is during spring and autumn migration. Although they weren’t tracking individual birds, collective sightings gave them an indication of how the species were migrating. They then used computer models to sort species with similar movement patterns into groups and compared migration routes with seasonal patterns of prevailing winds at night.

The study revealed that most US land birds fit into three main groups: a western one of 31 species, a central group of 17 species, and an eastern of 45 species. Examples of each group include the black-throated gray warbler, the clay-coloured sparrow, and the American redstart, respectively. The researchers noted that the flyways for these are much more spread out across the continent than those of wildfowl, and routes in the central and eastern groups overlap considerably.

The analysis also revealed that many more land birds than previously realised follow different routes through America in spring and autumn — particularly in the East, where many species cross the Gulf of Mexico in a single overnight flight.

Unlike wildfowl, which migrate north and south along the same relatively narrow routes, rather like lorries on a motorway, songbirds are more like passenger cars touring back roads. They are less tied to a single wetland habitat, so they can fan out. By shifting routes, birds take advantage of stronger tailwinds in spring and less severe headwinds in autumn. Tailwinds represent a huge advantage for small birds heading north to their breeding grounds, while finding weaker headwinds allows southbound birds to make the best of a bad situation.

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Frogs mating, and the bats danger


This video says about itself:

Risky Ripples

23 Jan 2014

When a male túngara frog serenades female frogs from a pond, he creates watery ripples that make him easier to target by rivals and predators such as bats. A túngara frog will stop calling if it sees a bat overhead, but ripples continue moving for several seconds after the call ceases. In the study, published Jan. 23, 2014 in the journal Science, researchers found evidence that bats use echolocation — a natural form of sonar — to detect these ripples and home in on a frog. The discovery sheds light on an ongoing evolutionary arms race between frogs and bats. Video by Wouter Halfwerk.

From The Why Files:

Menacing mating game: Frogs fear bats!

23 January 2014

Like any foolish fellow, the túngara frog lives and loves dangerously. To those in the tropical-bio-biz, it’s old news that this resident of shallow ponds ranging from Venezuela to Central Mexico is prey to frog-eating bats.

That croaking mating call makes a great target for the flying mammals with an appetite for frogs’ legs. But now we hear another reason why life is hard for the feckless frog.

In a study released today, scientists revealed that the croaking frog sends two separate signals to the bats: First, the mating call, which deters competing males while attracting females — and those hungry bats.

But the frogs power their croak by inflating and deflating an enormous air sac, which forms ripples on the pond that survive even after the frog chokes off its croaks after seeing a bat against the night sky

To test the interaction between the bats and frogs, first author Wouter Halfwerk of Leiden University in The Netherlands set up an experiment in Panama, using artificial frogs to simulate the appropriate sound, with or without ripples

Halfwerk and co-author Michael Ryan, professor of zoology at the University of Texas, found that bats would attack in response to the mating call alone, but the attacks increased 36 percent when ripples accompanied the soundtrack.

Frogs croak, and then croak!

This makes life difficult for the frogs, Ryan notes. To reproduce, they must call. “The males can stop calling, but they can’t take these ripples back, so the danger of calling extends for a few seconds. It’s amazing that bats are able to figure this out.”

The tests were held in darkness, so the bats must have been using their sonar — echolocation — to find the pattern of ripples.

The mating call is primarily to attract females, but it also shouts “Keep away!” to other males, and the competition doubled their “I’m here too!” responses when ripples followed the croaks. “If you look when they are calling, the frogs are spaced out,” Ryan says. “If another male is too close, they start to make aggressive calls, and sometimes they fight; I have seen them kill each other.”

Ryan, who first noticed the frog-bat system as a graduate student in the 1980s studying with bat biologist Merlin Tuttle, notes, “We have known for a long time that the bats can find the frogs.” The new study, however, is the first to show how waves created when the frog sounds off affects bats — and other frogs.

Now that they know that competing males are more responsive when ripples are present, the researchers plan to see how females act with and without ripples.

Live to love, but love to live!

If the bats have “cracked the code” of the frogs behavior, turning a mating move into a death dance, that could be shaping frog behavior. “We know frogs prefer calling under cover, compared to out in the open,” says Ryan. Not only do bats have trouble flying to the sheltered frogs, but they may also have difficulty detecting ripples with echolocation in the brush.

We mused: the frogs, like certain guys we could name, allow mating to trump everything, even mortal danger. “Through the entire animal kingdom — there are exceptions — but most of the attributes that make an animal sexy or beautiful can be very costly. Men die before women in part because testosterone has a negative effect on the immune system.”

Every time an animal communicates, it creates a disturbance in the environment, and that’s especially true for the “look-at-me” mating messages. “The question I have,” Ryan adds, “is how many of these incidental things that we animals do become fodder for another animal that is looking to parasitize, to lay eggs” or grab dinner?

Do some showboating, and a biological big brother may be bugging your channel, Ryan says. “Males have to make themselves more conspicuous to females; to call louder, to wear brighter colors, do fancy dances. But all of this also makes them more conspicuous to predators.”

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Maya and fake apocalypse


This video says about itself:

2012, NASA and the Mayan Calendar

Answers to some questions about 2012 from NASA’s Ask an Astrobiologist, Dr. David Morrison, and information about ancient Mayan calendars and their base 20 numerical system.

From Scientific American:

December 23, 2012

Maya Civilization Provides A Real Apocalyptic Lesson

Research shows that what laid low Mayan society was climate change, which brought prolonged drought. David Biello reports.

You survived the Mayan apocalypse, or at least transitioned to the next baktun, number 14 according to the Mayan calendar. But what real lessons does this ancient culture hold?

First and foremost, the Maya are a case study in adaptation. Their complex civilization of powerful city-states collapsed, and the jungle retook those urban centers. But the Mayan people endured, today being the principle ethnic population of parts of Mexico, Guatemala and Belize.

European invaders did not end the era of the Mayan city-state. Although it was descendants of those Europeans who came up with this apocalypse mumbo-jumbo.

Research shows that what laid low Mayan society was something more insidious: climate change. A subtle shift in weather patterns brought less rain and the Mayan civilization was simply unable to cope with a prolonged dry period punctuated by several severe droughts.

Given that our highly complex civilization is also facing climate change, it might make sense to look back to the Maya for a glimpse of our future. Today much of the former Mayan city-states are nature preserves, dotted by ruins. Will we do better when faced with crippling and long-lasting drought in this, the 14th baktun?

Mammals threatened by climate change


Mammals and storms, climate map

Mammals and drouight, climate map

From Wildlife Extra:

Disaster map predicts bleak future for mammals

Mammals are in for a stormy ride as cyclones and droughts caused by climate change could threaten populations

December 2012. Mammals could be at a greater risk of extinction due to predicted increases in extreme weather conditions according to some new research. Scientists have mapped out land mammal populations, and overlapped this with information of where droughts and cyclones are most likely to occur. This allowed them to identify species at high risk of exposure to extreme weather. The paper describes the results of assessing almost six thousand species of land mammals in this way.

Cyclones & droughts

Lead author of the paper, ZSL’s Eric Ameca y Juárez says: “Approximately a third of the species assessed have at least a quarter of their range exposed to cyclones, droughts or a combination of both. If these species are found to be highly susceptible to these conditions, it will lead to a substantial increase in the number of mammals classified as threatened by the IUCN under the category ‘climate change and severe weather’.”

Primates in particular are in danger

In particular, primates – already among the most endangered mammals in the world – are highlighted as being especially at risk. Over 90 per cent of black howler monkey (Alouatta pigra) and Yucatan spider monkey (Ateles geoffroyi yucatanensis) known habitats have been damaged by cyclones in the past, and studies have documented ways they are able to adapt to the detrimental effects of these natural disasters.

Madagascar

In contrast, very little is known about the impacts of these climatic extremes on other species. In Madagascar, entire known distributions of the western woolly lemur (Avahi occidentalis) and the golden bamboo lemur (Hapalemur aureus) have been exposed to both cyclones and drought. These endangered species are also amongst the world’s most evolutionary distinct, yet remain highly understudied.

ZSL’s research fellow Dr Nathalie Pettorelli says: “This is the first study of its kind to look at which species are at risk from extreme climatic events. There are a number of factors which influence how an animal copes with exposure to natural disasters. It is essential we identify species at greatest risk so that we can better inform conservation management in the face of global environmental change.”

The study was published by the Zoological Society of London (ZSL) in the journal Conservation Letters.