16 de agosto de 2022

We need to reflect on these turbulent times, where the climate is running wild in addition to viruses and war.

Global warming - well, it almost sounds banal - and the constant and relentless record-breaking heat waves yearly keep me awake. It is hoped that we are not heading for a turning point where much-needed measures that have long been envisaged will, if taken, be too late and no longer benefit.

Meanwhile, many leaders continue to watch these phenomena like rabbits watching a lightbox. Every minute, a forest the size of 40 football fields disappears on Earth.

Amazon forest under the management of President Balsenaro.

Our pigeons, very well adapted to heat, will undoubtedly suffer less than we, humanity, which is to blame for negligence.

The Columbia Livia (rock dove), from which our Columbia Livia domestic or domestic pigeon is descended, had a very efficient cooling system through water evaporation, which was up to 10 times more powerful than in the ordinary bird...

It is cool along a river or near a corn field because a lot of liquid water is evaporated into gaseous water vapour.

Once it is formed, water vapour particles move much further apart ( by 1.500 times) than in liquid water, containing much more energy. To achieve this state, this energy is extracted from the environment in the form of calories (heat), which cools the whole thing down (same system as a refrigerator). The (hot) air with the energy-rich evaporated water must be continuously discharged to keep the system running.

Simple representation: https://www.youtube.com/watch?v=DlfGwBC6MHU  

Slightly more complex: https://www.youtube.com/watch?v=XCWSP0Nil9M

"Entropy" is a notion in thermodynamics (part of physics) that studies this phenomenon. 

The water vapour molecules move much further apart (and therefore contain much more energy) than the liquid from which they evaporate.

The pigeon is facing significant challenges here. Heat can be dissipated by conduction(*), radiation, and convection at skin level. The expansion of the blood vessels helps with conduction. However, this is counteracted due to the insulation provided by the plumage. In the summer, the feathering is airy to allow better heat dissipation; in the winter, it is suitably closed and covered with sebum to optimise insulation.

Above all, the pigeon must evaporate water to cool down and save water, so it does not dry out. Evaporation can only take place via the mucous membranes of the respiratory tract. She can barely sweat (because there are no sweat glands on the skin) because the plumage would stick, and the wings would no longer work efficiently. (All this is controlled incredibly ingeniously by hormones, which we have discussed in previous blogs). All evaporation must therefore exit through the beak. They can accelerate the expulsion of air in case of excessive heat by rhythmic throat movements (similar to panting).

https://everythingnothuman.com/birds/how-do-birds-keep-cool/

Some breeds of pigeons in the southern hemisphere have adapted to very high desert temperatures and can still cool down by evaporating water on their skin (sweating). It enables them to regulate their temperature, e.g. during the breeding season. They managed to do so by modifying their skin structure (sweat glands).

This test is also revelatory. Two birds: our dove (Columba livia) and the partridge (Alectoris chukar), different in their habits and flying abilities, were compared in their ability to survive extremely high air temperatures. 

During 270-minute survival tests, both were exposed to air temperatures between 45 and 60°C and low relative humidity. The pigeon proved unique in its ability to survive 270 minutes of exposure to 60°C while regulating its body temperature at 43.8°C. The partridge could not survive 270 minutes of exposure to air temperatures above 48 °C.

The pigeons appeared exceptional in their capacity for cutaneous (skin) evaporation. Levels of up to 20.9 mg H2O/cm-2/hr were measured at 52 °C air temperature compared to 2.4 mg H2O/cm-2/hr in the partridge. The total evaporation of the pigeon exposed to 56°C air temperature was about 20% higher than that in the partridge. The maximum evaporation of the pigeon exposed to 60°C was 34.4 mg H2O/g/hour.

The significance of cutaneous (through the skin and not through the respiratory tract) water loss for survival during extremely high air temperatures is addressed.

It concludes that birds can be classified into two groups of their physiological ability to withstand heat stress:

• Most of the species studied use regular physiological mechanisms and are limited in their cooling capacity to withstand ambient temperatures of 48°C;

• Some bird species, including the pigeon, may have wide ecological distribution and are equipped with critical physiological adaptations to severe heat stress.
  

So pigeons are extraordinary survivors, and they can bring our overconfident to sometimes nonchalant and destructive attitude toward our beautiful planet to reason…

Let us reflect on their example. The moult and the shaping of the new plumage will be the next challenge. The significant temperature differences between day and night will become increasingly apparent in September. These differences influence the regulation of the body temperature, whereby the smooth changing of the plumage is essential.

The fancier's monitoring role during the moult is essential. He must balance out the extremes in the air temperature. He can protect the loft (close shutters) from the sharp drop in temperature at dawn. 

However, the loft should remain airy. Think of the constant temperature of the cave in which the ancestors of the homing pigeon lived. The (amount of) food (not enough food stops the moult), the temperature, the amount of light etc., all play a role in the smooth progress of the moult.

As outlined in previous blogs, various glands and their secreted hormones and enzymes also have a significant role to play.

All these subtle balances should take place in ideal conditions.

The new feathers are brighter in colour, purer in outline, silkier and shinier than the old ones. Their quality is an essential indication of the general state of health and condition. A dull plumage often indicates an underlying disease process or an unbalanced diet. Feathers also tell a story of the past season where (V-shaped) grooves can be read as marks of rather painful events for the pigeon.

Going for a long time without eating, significant fatigue and heavy medication remain "marked in the remiges". When we encounter abnormal (more than just a random ruptured vein) and difficult-to-form new "blood remiges", there is usually something fundamentally wrong (diet, disease of parasitic, bacterial origin).

The new winter plumage (*) will weigh thirty per cent heavier than the summer plumage and is denser. So material must be supplied. COMED's Murium was developed to meet all these characteristics.

Many fanciers have a good routine here and sense when something deserves more than ordinary attention. A rich moult mixture and good moult supplements are standard. Therefore choose the Comed moulting schedule in which extension three is strongly recommended.