IntegrityError: NOT NULL constraint failed with default=None, blank=True null=True in model?

I am running my script in the django shell, and the error is coming from these lines:

new_species = Species(genus=new_genus, species=row[4])
new_species.save()

This error:

IntegrityError: NOT NULL constraint failed: birds_species.species_english

I am trying to save information to this model:

class Species(models.Model):
    genus = models.ForeignKey(Genus, default=None)
    species = models.CharField(max_length=100, default=None)
    species_english = models.CharField(max_length=100, default=None, blank=True, null=True)

    def __str__(self):
        return self.species

I confirm that that migrations are up-to-date because I run the following lines in my django project:

$ python manage.py makemigrations birds
No changes detected in app 'birds'
$ python manage.py migrate
Operations to perform:
  Apply all migrations: sessions, admin, polls, auth, contenttypes, birds
Running migrations:
  No migrations to apply.

The problem is I am trying to save an object to the Species model, without defining the 1 column species_english. From the model it can be seen that I have default=None, blank=True, null=True which is what I thought we needed to allow null values by default. What do I have wrong here?

I am using the default sqlite3 DB for the DB backend.

Thanks!

EDIT

Here is the migration file contents:

# -*- coding: utf-8 -*-
# Generated by Django 1.9.2 on 2016-06-17 14:02
from __future__ import unicode_literals

from django.db import migrations, models


class Migration(migrations.Migration):

    dependencies = [
        ('birds', '0007_speciesfile'),
    ]

    operations = [
        migrations.AddField(
            model_name='species',
            name='species_english',
            field=models.CharField(blank=True, default=None, max_length=100, null=True),
        ),
    ]