Category Archives: Friends of Miles

Shark Skin: Milos Radakovich

Few creatures are more frightening
than sharks, but these complex fish
have also provided inspiration for several
useful technologies.

Throughout history, shark skin has
been used by many cultures, as sandpaper,
non-skid shoes, and the like. Swimsuits modeled on shark
skin are claimed to reduce drag by up to 4 percent. Now, synthetic
shark skin could make ships and submarines faster and
less expensive to operate.


The growth of barnacles, mussels, and algae increases drag by up
to 15 percent, and adds to fuel costs for commercial shipping
and the military.

Paints laced with copper curb the problem, but must be reapplied
periodically to be effective. They are expensive, and toxic
to other marine life. Fish, crabs, and whales are fouled by hitchhiking
marine life, but rarely sharks. Scientists have discovered
that part of the secret is in the complex design of their scales.

Shark scales are made of a hard material called dentin. Like tiny
teeth that all point backward, they make a shark feels smooth
from head to tail, but rough the other way. The scales flex individually,
limiting the amount of exposed surface area on which
organisms can attach. They also create tiny vortices that reduce
drag, making the shark faster and more energy efficient.


Barnacles make some of the strongest adhesives known, but the
glue can only penetrate so far into a rough surface, explaining
why scales can prevent them from sticking.

With the fake shark skin applied, a ship moving at 4-10 knots becomes
self-cleaning, leaving most fouling organisms in its wake.

Common Merganser: Dr J Murray Speirs

Common Merganser (male)

If you see a long, low, slim duck with an impossibly large brook of young hurrying along a rocky shoreline in summer, it is likely to be this species. Aggressive females “kidnap” youngsters from less aggressive mothers, so that broods of 30 or more are accumulated.

Common Merganser (female)

At most localities and in most seasons this is the common merganser in Ontario, although the Red-breasted Merganser may outnumber it at the height of their spring and fall migrations.

Common Mergansers Ashbridge’s Bay Park: Photo: Judy-Ann Cazemier

The long, low profile and “sawbill” beak identify it as a merganser. females look a good deal like female Red-breasted Mergansers but are somewhat larger, have a less shaggy crest and may be distinguished by the round white spot on the chin, contrasting with the reddish head and neck.

Common merganser (female)

Males lack the shaggy crest of the Red-breasted Merganser and show more white when resting on the water. In spring the white breast is suffused with a salmon pink “blush”.

Common Merganser (male)

Common Merganser family

Northern Rough-winged Swallow: Dr J Murray Speirs

Northern Rough-winged Swallow

This species is often found with the more familiar Bank Swallow but I associate it with smaller sand banks and frequently find it perched on dead twigs beside quiet waters.

Northern Rough-winged Swallow

It usually arrives about a week earlier in spring and stays longer in the fall than does the bank swallow.

Northern Rough-winged Swallow

It is not found so far north as is the Bank Swallow in Ontario and is less common even in the south. Most go to Central America for the winter.

Northern Rough-winged Swallows

This is the brown backed swallow known for its “dirty chin” lacking the pure white throat of the Bank Swallow and some brownish backed plumages of the Tree Swallow.

Northern Rough-winged Swallow

The Bank Swallow also sports a black “necklace” lacking in this species. When perched, the Rough-wing shows a suggestion of a crest. The usual flight note is a single “bzzt” not the chattery series of “bzzt”s given b y the Bank Swallow. In flight it glides frequently , with less fluttering than is usual with Bank Swallows.

Northern Rough-winged Swallows

It usually nests in the low cut banks of small streams, or in low road cuts though it may nest with Bank Swallows in larger sand banks. Not infrequently it nests in drainage tiles under bridges. In the hand the leading edge of the outer primary shows a series of hooklets; hence its name.

Northern Rough-winged Swallow

Dr J Murray Speirs

Scarlet Tanager: Dr J Murray Speirs

Scarlet Tanager (male)

Scarlet Tanagers often appear in southern Ontario in mid-May, before the trees are in leaf, when their brilliant plumage causes gasps of wonder in appreciative onlookers.

Scarlet Tanager (male)

On their breeding grounds, high in the maples in June , they are surprisingly hard to find and are usually located only by song or calls.

Scarlet Tanager (male)

By fall, much of their spring finery has been replaced by green and most pass by unnoticed, to winter in the tropical forests of South America.

Scarlet Tanager (male)

Males with their brilliant scarlet or vermilion bodies and contrasting black wings and tail, are easily identified.

Scarlet Tanager (male)

Females have green body plumage with dark brown wings and tail.

Scarlet Tanager (female) photo: National Audubon Society

The song is a hoarse robin-like carol and the call an emphatic “tip-her”.

Scarlet Tanager (male)

Dr J Murray Speirs

(I took the photos for this in the Don Valley in May 2018 : Miles Hearn)