Job 39:13-17 Gavest thou the goodly wings unto the peacocks? or wings and feathers unto the ostrich? Which leaveth her eggs in the earth, and warmeth them in dust, And forgetteth that the foot may crush them, or that the wild beast may break them. She is hardened against her young ones, as though they were not hers: her labour is in vain without fear; Because God hath deprived her of wisdom, neither hath he imparted to her understanding.
Lam. 4:3 Even the sea monsters draw out the breast, they give suck to their young ones: the daughter of my people is become cruel, like the ostriches in the wilderness.
Our question: Do these passages reflect a primitive, incorrect, belief about the ostrich?
Critics read these passages as saying that the ostrich is a stupid bird that lays its eggs on the ground, leaves them to be hatched by the heat of the sand, and then treats her young harshly after they have hatched. In contrast, they say that science texts describe the ostrich as a very caring parent. Laying eggs on the ground, rather than being a sign of neglect, is just something some birds normally do; and while the female may leave the nest, the male incubates the nest in her absence. Meanhile, when the young hatch, they are given watchful care by their mother.
Therefore, the critics say, the passages are in error: The ostrich's labor is not in vain.
Let's take a closer look at what these passages say, starting with Job. As a side note, Marvin Pope's commentary on Job  states that this section of Job is not in the LXX, and may not have been in the original text; but we will assume for the sake of argument that it was.
Which leaveth her eggs in the earth, and warmeth them in dust
Some translations render the word "leaveth" in terms of a forsaking. But the word here, 'azab, though it can carry that meaning, acquires that meaning based on context -- it carries the meaning of leaving behind, and no one would argue that the ostrich does not leave or place its eggs on the ground and leave them now and then (without "abandoning" them).
In fact, we'll see in a moment that this is a good description of their behavior, and indeed, even "forsaking" fits a certain behavior they have.
And forgetteth that the foot may crush them, or that the wild beast may break them.
Insofar as laying eggs on the ground is a risky procedure, none of this is untrue -- and it hardly counts as malicious or bad parenting. But there is actually more to this, and we will see that in a moment. Here are the two key passages:
Even the sea monsters draw out the breast, they give suck to their young ones: the daughter of my people is become cruel, like the ostriches in the wilderness.
Critics take this to be referring to a universal ostrich-ish practice, but there are indeed specific times when the ostrich will act this way. Provan's commentary on Lamentations , using Cramp's Handbook of the Birds of Europe, the Middle East, and North Africa as a source, notes:
Under certain environmental conditions...the family group may break up when chicks are a few weeks old, the adults renewing sexual activity and becoming highly aggressive towards all juveniles. Chicks fledged in small numbers outside the breeding season are frequently treated as outcasts and live solitarily.
And Eaton's Bible Dictionary reports another behavior:
The allusion here is to the habit of the ostrich with reference to its eggs, which is thus described: "The outer layer of eggs is generally so ill covered that they are destroyed in quantities by jackals, wild-cats, etc., and that the natives carry them away, only taking care not to leave the marks of their footsteps, since, when the ostrich comes and finds that her nest is discovered, she crushes the whole brood, and builds a nest elsewhere."
And here's something from another site now defunct:
Ostriches live in family groups consisting of one cock and several hens. During breeding season, the male will mate with the dominant female and one to four other hens. Each hen lays between two and eleven creamy white eggs in a communal nest which can be nearly 10 ft (3 m) across and is simply a hollow in the ground formed by scraping and body weight. When egg laying is complete there are usually ten to forty or more eggs in the nest; the most ever recorded was seventy-eight. Only about twenty can be incubated, however, so the dominant hen will reject any surplus eggs by pushing them out of the nest. She always ensures, however, that her own eggs remain.
Note that what we have here is a perfect example of the ostrich leaving -- indeed, forsaking -- the eggs "belonging" to her as dominant hen of the communal group, to the dust out where they can be trod upon.
Sounds pretty harsh. But even more so -- the site goes on:
The cocks and the hens take it in turns to incubate the eggs; the hens sit on them during the day and the cocks at night. This shift system lasts for an average of forty-two days until the eggs hatch. When the chicks emerge into the world, it is the male who cares for them.
So it seems momma is "hardened" against her young ones after all -- Dad is the one who does the job of parenting after hatching.
The behavior with eggs is even further confirmed by Brian C. R. Bertram's The Ostrich Communal Nesting System (1992). Among the relevant points offered by Bertram:
- Ostriches definitely "leave" their nests -- in a study of 57 nests, Bertram found that "most were destroyed by predators after surviving for different and unpredictable periods of time."  As a result, "The great majority of ostrich nests did not produce any chicks, mainly because of predation."  Only 5 out of 57 had successful hatchings. 
- The secondary female ostriches -- what Bertram calls "minor hens" -- laid eggs in the nest, but thereafter "took no part in attending or guarding it, nor later in incubating it."  This sounds like "forsaking" and "cruel" behavior, subjectively speaking, to me.
- Bertram confirms the behavior of shoving the eggs of minor hens out of the nest as needed for space; only 20 eggs at most could be covered. This happened "at most incubating nests" . The eggs shoved out "eventually rotted or were destroyed." 
- The male spends 71% of the incubating time on the nest; the major hen, 29%; the minor hens, as noted above, none.
So let's review:
Which leaveth her eggs in the earth -- this would be a perfect description of what is done to the outer ring of "forsaken" eggs, which are the communal property of the group under the discretion of the major hen.
and warmeth them in dust -- Note that the word "warmeth" here is not term-specific for incubation -- it simply means "heats" (Ex. 16:21 And they gathered it every morning, every man according to his eating: and when the sun waxed hot (chamam), it melted.) Ostrich incubation actually is for the purpose of cooling the eggs, not warming them. This again describes the outer ring of forsaken eggs.
And forgetteth that the foot may crush them, or that the wild beast may break them. The word "foregetteth" indicates an obliviousness or apathy -- we have seen that the major hen purposely pushes these eggs out and doesn't care about what happens to them; she is preserving her own eggs.
She is hardened against her young ones, as though they were not hers: her labour is in vain without fear. We have seen how this applies to the chicks.
The daughter of my people is become cruel, like the ostriches in the wilderness. Same here; we have enough data for a subjective judgment of this sort.
So the behaviors described would suit our passages.