The question is... if a bird is confronted with a cloud barrier where their way is blocked do they avoid cloud completely or do they have the ability to fly on through... who really knows other than the birds. The main reason why I think it is unlikely is because visual cues are needed to to maintain level flight and in cloud visual information is usually totally absent. However clouds also create additional dangers for birds such as strong wind shears, lightning, hail and loss of visual navigation information. Most birds can avoid the problem anyway by staying low down close to the ground or water or simply landing and waiting for the bad weather to pass.
A Bar-tailed Godwit at the Shoalhavn River in NSW. These migrants make some of the longest non-stop overwater migrations of any bird species. They optimize their flight endurance by flying at high altitudes but flying up high creates challenges from encounters with cloud barriers across their flight paths...
Clouds over South Australia. Even this Qantas jet altered it's flight path to avoid this band of frontal cumulus.
The climate debate has focussed our attention more and more on the air above us. It’s not actually carbon dioxide in the atmosphere that is the problem... its water. Water in its three states; water vapour (which we can’t see), liquid water in the form of rain and minute droplets that makeup most low level clouds and solid water in the form of the ice clouds of the high altitude cirrus layers as well as ice falling as snow and hail. According to P. H. Gleick in the Encyclopedia of Climate and Weather there is 12,900 cubic kilometers of water in the atmosphere at any one time... and that’s a lot of water. The problem is for people and birds alike is there is often either too much or not enough.
Most migrants travel north south however Double-banded Plovers make east west migrations back and forth across the Tasman Sea between Australia and New Zealand.
Climate change is a fact... it’s been going on for millions of years. Even if we were to somehow magically neutralise all human carbon emissions climate change would continue as it has in the past. I don't like the focus on carbon as the silver bullet of environmental change... I belive "sustainability" is a better catchword because we need sustainability in all things not just carbon... anyway, anyway... moving on...
Here in Australia in the southern summer of 2013 and now continuing well into the autumn, water in the atmosphere has had dramatic and contrasting results. The centre of Australia has been largely cloudless because of a lack of moisture in the airmass above the continent. The Red Centre has baked day after day under a relentless sun. And as this hot air moves south it continues to create record temperatures. And while the lack of atmospheric moisture continues to affect much of the continent, to the northeast cyclonic and low pressure systems have brought the opposite... huge floods along the coasts of Queensland and NSW.
Clear skies over much of Australia brought about by the lack of moisture in the atmosphere have created record high temperatures.
Air ain't just air... looking up in the sky on any one day we might see lots of stuff up there; party balloons, birds, dust, aeroplanes, rainbows, helicopters, a cow or two (having jumped over the moon), sheets of corrugated iron (from tornados), base jumpers, kites, con-trails, aliens departing at warp speed after doing intergalactic work experience for their art major on a crop of wheat... ￼
After a cloudless day on the north Pilbara coast a band of small cumulus clouds appears. The clouds we see give us a clue to what is going on in the air above us... we just have to look and try to understand what the clouds are telling us about not only what is happening now but in the future as well. Birds use their powers of observation of the weather to help them; swifts track frontal changes... pelicans and avocets seem to know, despite being hundreds of kilometers away, that the normally dry Lake Eyre in the middle of Australia is flooding and congregate in vast numbers to breed.
The vanguard clouds of Cyclone Peta move westwards along the Western Australian coast. Cyclones bring strong winds, torrential rain and tidal surges threatening coastal areas. Inland they loose strength and become rain depressions but still are powerful enough to cause widespread flooding.
The windsock silhouetted against the sunrise at Tooradin Airport on the edge of Western Port Bay in southern Victoria. Pilots use a windsock to tell them what the wind direction and strength is on the ground but what's going on above may be completely different.
Finding out just what part of the sky birds occupy when they are flying is actually quite difficult, especially for those birds that fly well above the ground. However, pilots provide us with some of the clues to where birds are and when. And they do that as a result of reporting bird strikes. It is actually surprising that there is not more bird strikes considering that in the USA it is estimated that more than five billion birds migrate southwards each fall and return back in the spring. According to the International Bird Strike Committee which researches bird strikes estimates that about 75% of strikes occur at less than 500 feet above ground level and 41% in the vicinity of an airport.
This Southern Royal Albatross is getting air-borne from the ocean south of Port MacDonnell in South Australia. It remains at sea for long periods but is able to mitigate the effects of reduced vision in clouds by flying close to the surface where it can still see as well as having the ability to land on the surface of the sea and wait it out.
In the USA in the years 1990 to 1998 there were 22,935 reported wildlife strikes on aircraft of which 585 were mammals. Mammals generally live on the ground, apart from cows returning from jumping over the moon and bats. Aircraft strike deer, kangaroos, coyotes, bats, foxes, rabbits and even alligators... but by far the majority are birds. So if we were to accept that 5 billion birds migrate back and forth each year in the USA then over that same nine year period there were 90 billion individual birds migration flights and only 22,320 twenty encounters resulting in impacting an aircraft. Roughly one bird strike for every 4,032,258 individual migration flights and as many of those bird strikes would have involved non-migrating resident birds the chances of hitting a migrating bird are even less. Clearly, apart from around airports, birds and aircraft don’t occupy the same airspace... much.
The sky above Wilson’s Prom in Victoria gives us clues to the complex nature of the atmosphere above.
A Jetstar A330 becomes airborne at Sydney's Kingsford Smith Airport.
Generally aircraft only fly below 500 feet for taking off or landing. They climb rapidly to altitudes well above 30,000 ft well out of the range of most birds. Likewise they descend relatively steeply to minimize the amount of time at low level. Aircraft can fly faster and use substantially less fuel by keeping as high as possible for as long as possible. Fortunately for the birds and air travelers, birds are down low and aircraft are up high. Having said that the highest bird strike reported so far involves a Ruppeli’s Vulture and a commercial jet airliner that occurred over the Cote d’Ivoire at the astonishing altitude of 37,000 feet (11,300 m).
Osprey vs Osprey... maybe... on the 24th November 1987 an amatuer built Osprey aeroplane struck a bird on take-off near Cape Liptrap in Victoria. The bird shattered the windscreen and impaired the pilot's vision. The pilot was able to land the aircraft but it caught fire thought to have ben caused by the bird rupturing the fuel line. Hstory doesn't record whether the unfortunate bird was an Osprey but it would be kind of endocentric.
While it is likely that most birds fly at low level there are good reasons for migrating birds to go higher. Like aircraft birds can fly faster at height because of the reduction in air density that occurs as altitude increases. They can also take advantage of more stronger winds as wind speed generally increases with altitude. Wind can have a substantial benefit for migrating birds. This of course is a double-edged sword if the wind happens to be coming from the opposite direction.
What is enlightening is that very few if any bird strikes occur in cloud. They occur almost without exception in clear air... to be continued...
The first post can be found at the following link...