Alder

Body: Peacock Herl

Hackle: Brown or Black

Wing: Brown Mottled Turkey

Head: Black

I had also collected information related to the Erlkonig, partially overlapping some of the ones that were mentioned in the Pale Fire Notes & references:found in the internet. As the one below:
Selected German Verse by J.W. Goethe - Erlkönig/Erlking (1782) von Johann Wolfgang von Goethe
In German and Scandinavian mythology, an “Erlkönig” is an evil spirit that lurks about to threaten humans, especially children. It has often been claimed that Goethe's term Erlkönig is a German mistranslation of the Danish “ellerkonge” or “elverkonge” or “king of the elves,” but in fact this may not be the case. In an interesting German article on the topic, Burkhard Schröder claims that Goethe knew exactly what he was doing, and the term Erlkönig can be traced back to an ancient Greek goddess of death (Todesgöttin) known as Alphito, who became a female Erlkönigin as she moved north, and even the biblical Lilith. (For more, see German Myth 9 in our Misnomers, Myths, and Misconceptions section.)

Wer reitet so spät durch Nacht und Wind?   Who rides so late through the night and wind?
Es ist der Vater mit seinem Kind;                 It's the father with his child;
Er hat den Knaben wohl in dem Arm,         He has the boy safe in his arm,
Er faßt ihn sicher, er hält ihn warm.             He holds him secure, he holds him warm.
 
«Mein Sohn, was birgst du so bang dein Gesicht?»                 –“My son, what makes you hide your face in fear?” –
Siehst, Vater, du den Erlkönig nicht?                                      Father, don't you see the Erlking?
Den Erlenkönig mit Kron und Schweif?                                –The Erlking with crown and flowing robe? –
«Mein Sohn, es ist ein Nebelstreif.»                                        –“My son, it's a wisp of fog.” –
 
«Du liebes Kind, komm, geh mit mir!                                   “You dear child, come along with me!
Gar schöne Spiele spiel' ich mit dir;                                        Such lovely games I'll play with you;
Manch bunte Blumen sind an dem Strand,                            Many colorful flowers are at the shore,
Meine Mutter hat manch gülden Gewand.»                          My mother has many a golden garment.”
 
Mein Vater, mein Vater, und hörest du nicht,                       My father, my father, and do you not hear
Was Erlenkönig mir leise verspricht?                                    –What the Erlking promises me so softly? –
«Sei ruhig, bleibe ruhig, mein Kind;                                      “Be quiet, stay quiet, my child;
In dürren Blättern säuselt der Wind.»                                   –In the dry leaves the wind is rustling.” –
 
«Willst, feiner Knabe, du mit mir gehn?                              “Won't you come along with me, my fine boy?
Meine Töchter sollen dich warten schön;                            My daughters shall attend to you so nicely.
Meine Töchter führen den nächtlichen Reihn,                    My daughters do their nightly dance,
Und wiegen und tanzen und singen dich ein.»                    And they'll rock you and dance you and sing you to sleep.”
 
Mein Vater, mein Vater, und siehst du nicht dort                My father, my father, and do you not see over there
Erlkönigs Töchter am düstern Ort?                                    –Erlking's daughters in that dark place? –
«Mein Sohn, mein Sohn, ich seh es genau:                          “My son, my son, I see it most definitely:
Es scheinen die alten Weiden so grau.»                               It's the willow trees looking so grey.”
 
«Ich liebe dich, mich reizt deine schöne Gestalt;                “I love you; I'm charmed by your beautiful form;
Und bist du nicht willig, so brauch ich Gewalt.»                  And if you're not willing, then I'll use force.”
Mein Vater, mein Vater, jetzt faßt er mich an!                    My father, my father, now he's grabbing hold of me!
Erlkönig hat mir ein Leids getan!                                       –Erlking has done me harm! –
 
Dem Vater grausets, er reitet geschwind,                          The father shudders, he rides swiftly,
Er hält in Armen das ächzende Kind,                               He holds in (his) arms the moaning child.
Erreicht den Hof mit Mühe und Not;                              He reaches the farmhouse with effort and urgency.
In seinen Armen das Kind war tot.                                  In his arms the child was dead. (Translation by Hyde Flippo)