: Argentine Ornithology, Volume I (of 2) by P. L Sclater, W. H Hudson (books to read in your 20s female .txt) 📖

warned of danger. Consider the different

behaviour of three species that seldom or never warn their offspring of

danger. The young of _Synallaxis spixi_, though in a deep domed nest,

will throw itself to the ground, attempting thus to make its escape.

The young of _Mimus patagonicus_ sits close and motionless, with closed

eyes, mimicking death. The young of our common _Zenaida_, even before

it is fledged, will swell itself up and strike angrily at the intruder

with beak and wings; and, by making so brave a show of its inefficient

weapons, it probably often saves itself from destruction. But any thing

approaching the young _Molothrus_ is welcomed with fluttering wings and

clamorous cries, as if all creatures were expected to minister to its

necessities.

 

December 24.--To-day I found a young _Molothrus_ in the nest of

_Spermophila cærulescens_; he cried for food on seeing my hand approach

the nest; I took him out and dropped him down, when, finding himself on

the ground, he immediately made off, half-flying. After a hard chase I

succeeded in recapturing him, and began to twirl him about, making him

scream, so as to inform his foster-parents of his situation, for they

were not by at the moment. I then put him back in, or rather upon, the

little cradle of a nest, and plucked half-a-dozen large measure-worms

from an adjacent twig. The worms I handed to the bird as I drew them

from the cases, and with great greediness he devoured them all,

notwithstanding the ill-treatment he had just received, and utterly

disregarding the wild excited cries of his foster-parents, just arrived

and hovering within three or four feet of the nest.

 

Last summer I noticed a young Cow-bird in a stubble-field, perched on

the top of a slender dry stalk; as it was clamouring at short intervals,

I waited to see what bird would come to it. It proved to be the

diminutive _Hapalocercus flaviventris_; and I was much amused to see the

little thing fly directly to its larger foster-offspring and, alighting

on its back, drop a worm into the upturned open mouth. After remaining a

moment on its singular perch, the Flycatcher flew away, but in less than

half a minute returned and perched again on the young bird's back. I

continued watching them until the _Molothrus_ flew off, but not before I

had seen him fed seven or eight times in the same manner.

 

In the foregoing anecdotes may be seen the peculiar habits of the young

_Molothrus_. As the nests in which it is hatched, from those of the

little _Serpophaga_ and Wren to those of _Mimus_, vary so much in size

and materials, and are placed in such different situations, the young

_Molothrus_ must have in most of them a somewhat incongruous appearance.

But in the habits of the young bird is the greatest incongruity or

inadaptation. When the nest is in a close thicket or forest, though much

too small for the bird, and although the bird itself cannot understand

its foster-parents, and welcomes all things that, whether with good or

evil design, come near it, the unfitness is not so apparent as when the

nest is in open fields and plains.

 

The young _Molothrus_ differs from the true offspring of its

foster-parents in its habit of quitting the nest as soon as it is

able, trying to follow the old bird, and placing itself in the most

conspicuous place it can find, such as the summit of a stalk or weed,

and there demanding food with frequent and importunate cries. Thus the

little Flycatcher had acquired the habit of perching on the back of its

charge to feed it, because parent birds invariably perch above their

young to feed them, and the young Cow-bird prevented this by always

sitting on the summit of the stalk it perched on. The habit is most

fatal on the open and closely cropped pampas inhabited by the Cachila

(_Anthus correndera_). In December, when the Cachila Pipit rears its

second brood, the _Milvago chimango_ also has young, and feeds them

almost exclusively on the young of various species of small birds. At

this season the Chimango destroys great numbers of the young of the

Cachila and of _Synallaxis hudsoni_. Yet these birds are beautifully

adapted in structure, coloration, and habits to their station. It thus

happens that in districts where the _Molothrus_ is abundant, their eggs

are found in a majority of the Cachilas' nests: and yet to find a young

Cow-bird out of the nest is a rare thing here, for as soon as the young

birds are able to quit the nest and expose themselves they are all or

nearly all carried off by the Chimangos.

 

 

_Conjectures as to the Origin of the Parasitic Instinct in_ M.

bonariensis.

 

Darwin's opinion that the "immediate and final cause of the Cuckoo's

instinct is that she lays her eggs not daily, but at intervals of two

or three days" ('Origin of Species'), carries no great appearance of

probability with it; for might it not just as reasonably be said that

the parasitic instinct is the immediate and final cause of her laying

her eggs at long intervals? If it is favourable to a species with the

instinct of the Cuckoo (and it probably is favourable) to lay eggs at

longer intervals than other species, then natural selection would avail

itself of every modification in the reproductive organs that tended to

produce such a result, and make the improved structure permanent. It

is said ('Origin of Species,' chapter vii.) that the American Cuckoo

lays also at long intervals, and has eggs and young at the same

time in its nest, a circumstance manifestly disadvantageous. Of the

_Coccyzus melanocoryphus_, the only one of our three _Coccyzi_ whose

nesting-habits I am acquainted with, I can say that it never begins to

incubate till the full complement of eggs are laid--that its young are

hatched simultaneously. But if it is sought to trace the origin of the

European Cuckoo's instinct in the nesting-habits of American _Coccyzi_,

it might be attributed not to the aberrant habit of perhaps a single

species, but to another and more disadvantageous habit common to

the entire genus, viz., their habit of building exceedingly frail

platform-nests from which the eggs and young very frequently fall. By

occasionally dropping an egg in the deep, secure nest of some other

bird, an advantage would be possessed by the birds hatched in them, and

in them the habit would perhaps become hereditary. Be this as it may

(and the one guess is perhaps as wide of the truth as the other), there

are many genera intermediate between _Cuculus_ and _Molothrus_ in which

no trace of a parasitic habit appears; and it seems more than probable

that the analogous instincts originated in different ways in the two

genera. As regards the origin of the instinct in _Molothrus_, it will

perhaps seem premature to found speculations on the few facts here

recorded, and before we are acquainted with the habits of other members

of the genus. That a species should totally lose so universal an

instinct as the maternal one, and yet avail itself of that affection in

other species to propagate itself, seems a great mystery. Nevertheless,

I cannot refrain from all conjecture on the subject, and will go so far

as to suggest what may have been at least one of the many concurrent

causes that have produced the parasitic instinct. The apparently

transitional nesting-habits of several species, and one remarkable habit

of _M. bonariensis_, seem to me to throw some light on a point bearing

intimately on the subject, viz., the loss of the nest-making instinct in

this species.

 

Habits vary greatly; were it not so, they would never seem so well

adapted to the conditions of life as we find them, since the conditions

themselves are not unchangeable. Thus it happens that, while a species

seems well adapted to its state in its habits, it frequently seems not

so well adapted in its relatively immutable structure. For example,

without going away from the pampas, we find a Tringa with the habits of

an upland Plover, a Tyrant-bird (_Pitangus bellicosus_) preying on mice

and snakes, another Tyrant-bird (_Myiotheretes rufiventris_) Plover-like

in its habits, and finally a Woodpecker (_Colaptes campestris_) that

seeks its food on the ground like a Starling; yet in none of these--and

the list might be greatly lengthened--has there been anything like a

modification of structure to keep pace with the altered manner of life.

But, however much the original or generic habits of a species may have

become altered--the habits of a species being widely different from

those of its congeners, also a want of correspondence between structure

and habits (the last being always more suited to conditions than the

first) being taken as evidence of such alteration--traces of ancient and

disused habits frequently reappear. Seemingly capricious actions too

numerous, too vague, or too insignificant to be recorded, improvised

definite actions that are not habitual, apparent imitations of the

actions of other species, a perpetual inclination to attempt something

that is never attempted, and attempts to do that which is never

done--these and other like motions are, I believe, in many cases to be

attributed to the faint promptings of obsolete instincts. To the same

cause many of the occasional aberrant habits of individuals may possibly

be due--such as of a bird that builds in trees occasionally laying

on the ground. If recurrence to an ancestral type be traceable in

structure, coloration, language, it is reasonable to expect something

analogous to occur in instincts. But even if such casual and often

aimless motions as I have mentioned should guide us unerringly to the

knowledge of the old and disused instincts of a species, this knowledge

of itself would not enable us to discover the origin of present ones.

But assuming it as a fact that the conditions of existence, and the

changes going on in them, are in every case the fundamental cause of

alterations in habits, I believe that in many cases a knowledge of the

disused instincts will assist us very materially in the inquiry. I will

illustrate my meaning with a supposititious case. Should all or many

species of _Columbidæ_ manifest an inclination for haunting rocks and

banks, and for entering or peering into holes in them, such vague and

purposeless actions, connected with the facts that all Doves build

simple platform-nests (like _Columba livia_ and others that build on a

flat surface), also lay white eggs (the rule being that eggs laid in

dark holes are white, exposed eggs coloured), also that one species, _C.

livia_, does lay in holes in rocks, would lead us to believe that the

habit of this species was once common to the genus. We should conclude

that an insufficiency of proper breeding-places, _i. e._ new external

conditions, first induced Doves to build in trees. Thus _C. livia_ also

builds in trees where there are no rocks; but, when able, returns to its

ancestral habits. In the other species we should believe the primitive

habit to be totally lost from disuse, or only to manifest itself in a

faint uncertain manner.

 

Now, in _Molothrus bonariensis_ we see just such a vague, purposeless

habit as the imaginary one I have described. Before and during the

breeding-season the females, sometimes accompanied by the males, are

seen continually haunting and examining the domed nests of some of the

Dendrocolaptidæ. This does not seem like a mere freak of curiosity,

but their persistence in their investigations is precisely like that

of birds that habitually make choice of such breeding-places. It is

surprising that they never do actually lay in such nests, except when

the side or dome has been accidentally broken enough to admit the light

into the interior. Whenever I set boxes up in my trees, the female

Cow-birds were the first to visit them. Sometimes one will spend half a

day loitering about and inspecting a box, repeatedly climbing round

and over it, and always ending at the entrance, into which she peers

curiously, and when about to enter starting back, as if scared at the

obscurity within. But after retiring a little space she will return

again and again, as if fascinated with the comfort and security of such

an abode. It is amusing to see how pertinaciously they hang about the

ovens of the Oven-birds, apparently determined to take possession of

them, flying back after a hundred repulses, and yet not entering them

even when they have the opportunity. Sometimes one is seen following a

Wren or a Swallow to its nest beneath the eaves, and then clinging to

the wall beneath the hole into which it disappeared. I could fill many

pages with instances of this habit of _M. bonariensis_, which, useless

though it be, is as strong an affection as the bird possesses. That it

is a recurrence to a long disused habit, I can scarcely doubt; at least,

to no other cause that I can imagine can it be attributed; and, besides,

it seems to me that