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

the nest of _M. badius_, unless it be in a forsaken nest! Perhaps

it will be difficult for naturalists to believe this; for if the

_M. badius_ is so excessively vigilant and jealous of other birds

approaching its nest as to succeed in keeping out the subtle, silent,

grey-plumaged, omnipresent female _M. bonariensis_, why does it not also

keep off the far rarer, noisy, bustling, conspicuously coloured _M.

rufoaxillaris_? I cannot say. The only explanation that has occurred to

me is that _M. badius_ is sagacious enough to distinguish the eggs of

the common parasite, and throws them out of its nest. But this is

scarcely probable, for I have hunted in vain under the trees for the

ejected eggs; and I have never found the eggs of _M. badius_ with holes

pecked in the shells, which would have been the case had a _M.

bonariensis_ intruded into the nest.

 

With the results just recorded I felt more than satisfied, though so

much still remained to be known; and I looked forward to the next summer

to work out the rich mine on which I had stumbled by chance. Unhappily,

when spring came round again ill-health kept me a prisoner in the city,

and finding no improvement in my condition, I eventually left Buenos

Ayres at the close of the warm season to try whether change of climate

would benefit me. Before leaving, however, I spent a few days at home,

and saw enough then to satisfy me that my conclusions were correct. Most

of the birds had finished breeding, but while examining some nests of

_Anumbius_ I found one which Bay-wings had tenanted, and which for some

reason they had forsaken leaving _ten_ unincubated eggs. They were all

like Bay-wings' eggs, but I have no doubt that five of them were eggs of

_M. rufoaxillaris_. During my rides in the neighbourhood I also found

two flocks of Bay-wings, each composed of several families, and amongst

the young birds I noticed several individuals beginning to assume the

purple plumage, like those of the previous autumn. I did not think it

necessary to shoot more specimens.

 

The question, why _M. badius_ permits _M. rufoaxillaris_ to use its

nest, while excluding the allied parasite, _M. bonariensis_, must

be answered by future observers; but before passing from this very

interesting group (_Molothrus_) I wish to make some general remarks on

their habits and their anomalous relations to other species.

 

It is with a considerable degree of repugnance that we regard the

parasitical instincts in birds; the reason it excites such a feeling is

manifestly because it presents itself to the mind as--to use the words

of a naturalist of the last century, who was also a theologian, and

believed the Cuckoo had been created with such a habit--"a monstrous

outrage on the maternal affection, one of the first great dictates of

nature." An _outrage_, since each creature has been endowed with this

all-powerful affection for the preservation of its own, and not another,

species; and here we see it, by a subtle process, an unconscious

iniquity, turned from its purpose, perverted and made subservient to the

very opposing agency against which it was intended as a safeguard!

The formation of such an instinct seems indeed like an unforeseen

contingency in the system of nature, a malady strengthened, if not

induced, by the very laws established for the preservation of health,

and which the _vis medicatrix_ of nature is incapable of eliminating.

Again, the egg of a parasitical species is generally so much larger,

differing also in coloration from the eggs it is placed with, whilst

there is such an unvarying dissimilarity between the young bird and

its living or murdered foster-brothers, that, unreasoning as we know

instinct, and especially the maternal instinct, is, we are shocked at

so glaring and flagrant an instance of its blind stupidity.

 

In the competition for place, the struggle for its existence, said with

reason to be most deadly between such species as are most nearly allied,

the operations are imperceptible, and the changes are so gradual,

that the diminution and filial disappearance of one species is never

attributed to a corresponding increase in another more favoured species

over the same region. It is not as if the regnant species had invaded

and seized on the province of another, but appears rather as if they had

quietly entered on the possession of an inheritance that was theirs by

right. Mighty as are the results worked out by such a process, it is

only by a somewhat strained metaphor that it can be called a _struggle_.

But even when the war is open and declared, as between a raptorial

species and its victims, the former is manifestly driven by necessity.

And in this case the species preyed on are endowed with peculiar

sagacity to escape its persecutions; so that the war is not one of

extermination, but, as in a border war, the invader is satisfied with

carrying off the weak and unwary stragglers. Thus the open, declared

enmity is in reality beneficial to a species; for it is sure to cut

off all such individuals as might cause its degeneration. But we can

conceive no necessity for such a fatal instinct as that of the Cuckoo

and Cow-bird destructive to such myriads of lives in their beginning.

And inasmuch as their preservation is inimical to the species on which

they are parasitical, there must also here be a struggle. But what kind

of struggle? Not as in other species, where one perishes in the combat

that gives greater strength to the victor, but an anomalous struggle in

which one of the combatants has made his adversary turn his weapons

against himself, and so seems to have an infinite advantage. It is

impossible for him to suffer defeat; and yet, to follow out the

metaphor, he has so wormed about and interlaced himself with his

opponent that as soon as he succeeds in overcoming him he also must

inevitably perish. Such a result is perhaps impossible, as there are so

many causes operating to check the undue increase of any one species:

consequently the struggle, unequal as it appears, must continue for

ever. Thus, in whatever way we view the parasitical habit, it appears

cruel, treacherous, and vicious in the highest degree. But should we

attempt to mentally create a perfect parasitical instinct (that is, one

that would be thoroughly efficient with the least possible prejudice

to or injustice towards another species; for the preservation of the

species on which the parasite is dependent is necessary to its own) by

combining in imagination all known parasitical habits, eliminating every

offensive quality or circumstance, and attributing such others in their

place as we should think fit, our conception would probably still fall

short in simplicity, beauty, and completeness of the actual instinct of

_M. rufoaxillaris_. Instead of laying its eggs promiscuously in every

receptacle that offers, it selects the nest of a single species; so that

its selective instinct is related to the adaptive resemblance in its

eggs and young to those of the species on which it is parasitical. Such

an adaptive resemblance could not of course exist if it laid its eggs in

the nests of more than one species, and it is certainly a circumstance

eminently favourable to preservation. Then, there not being any such

incongruity and unfitness as we find in nests into which other parasites

intrude, there is no reason here to regard the foster-parents' affection

as blind and stupid; the similarity being close enough to baffle the

keenest sagacity. Nor can the instinct here appear in the light of an

outrage on the maternal affection; for the young _M. rufoaxillaris_

possesses no advantage over its foster-brothers. It is not endowed

with greater strength and voracity to monopolize the attentions of

the foster-parent or to eject the real offspring; but being in every

particular precisely like them, it has only an equal chance of being

preserved. To this wonderful parasitical instinct we may well

apply Darwin's words, when speaking of the architecture of the

hive-bee:--"Beyond this stage of perfection natural selection could

not lead."

96. MOLOTHRUS BADIUS, Vieill. (BAY-WINGED COW-BIRD.) [Plate VI. Fig. 1.]

 

+Molothrus badius+, _Burm. La-Plata Reise_, ii. p. 495 (Paraná and

      Tucuman). _Scl. et Salv. Nomencl._ p. 37; _Hudson, P. Z. S._

      1874, p. 163 (Buenos Ayres); _Durnford, Ibis_, 1877, p. 174

      (Buenos Ayres); _Scl. Cat. B._ xi. p. 338.

 

    _Description._--Dull grey, beneath rather paler; wings chestnut;

    tips of primaries, inner portions of secondaries, and tail blackish;

    bill and feet black: total length 7·6 inches, wing 3·5, tail 3·0.

    _Female_ similar.

 

_Hab._ Argentina, Paraguay, and Bolivia.

 

In this species the sexes are alike; the plumage of the body is

grey-drab colour, with a black spot between the eye and beak; tail

dark, the quills cinnamon-colour; beak and legs black. Azara describing

it under the name of _Tordo pardo roxiso_, says it is a rare bird, so

that it has probably greatly increased since his time, as it is now

quite common in the Plata district.

 

The Bay-wings usually go in small flocks, numbering from ten to thirty

individuals, and are not migratory, but in winter they travel about a

great deal from place to place without extending their journeys more

than a few miles in any direction. They are fond of coming about houses,

and are frequently seen pecking at the fresh meat hanging out of doors;

and, like other birds of the same tribe, feed chiefly on the ground.

They spend a great portion of their time on trees, are familiar with man

and inactive, and in their motions singularly slow and deliberate. Their

language is varied. Curiosity or alarm is expressed by trilling notes,

and before quitting a tree all the birds of a flock ceremoniously invite

each other to fly with long clear notes, powerful enough to be heard a

quarter of a mile away.

 

They also sing a great deal in all seasons, the song being composed

of soft, clear, rather sweet notes, variously modulated, uttered in a

leisurely manner, and seeming to express a composed frame of mind, all

the birds in a flock singing in concert. During the cold season the

flock always finds some sheltered sunny spot on the north side of a

woodpile or hedge, where they spend several hours every day, sitting

still and singing in their usual quiet, soft style.

 

Their extreme sociability affects their breeding-habits, for sometimes

the flock does not break up in spring, and several females lay in

one nest together; but whether the birds are paired or practice a

promiscuous intercourse, I have not been able to discover. They have

a great partiality for the large domed nests made by the _Anumbius

acuticaudatus_, called Leñatero in the vernacular. One summer a flock of

about ten Bay-wings took possession of a Leñatero's nest on one of my

trees, and after a few days I took fourteen eggs from it. Though the

birds hopped, chirping round me, manifesting great solicitude, the eggs

were quite cold, and had I left them many more would have been laid, no

doubt; but as they were piled up three or four deep in the nest they

could never have been hatched.

 

As a rule, however, the flock breaks up into pairs; and then a neat,

well-made nest is built in the fork of a branch, lined with horsehair;

or, oftener still, a Leñatero's nest is seized, the Bay-wings fighting

with great spirit to get possession, and in it, or on it, their own nest

is made. Like their relations, the Common Cow-bird, they seem strongly

attracted by domed nests, and yet shrink from laying in the dark

interior; as a rule when they have captured a Leñatero's nest they break

a hole in the side and so admit the light and form an easy entrance.

One summer a pair of Bay-wings attacked a Leñatero's nest on one of my

trees; the fighting was kept up for three or four days, and then at the

foot of the tree I found five young Leñateros, fully fledged, which had

been pecked to death and thrown out of the nest.

 

The eggs of the Bay-wing are five in number, nearly round, and