Cannot make development database with rake - ruby-on-rails-3

Question

Update: Running
RAILS_ENV=development rake db:create
... works. But the rake commands without the RAILS_ENV prefix don't. What gives?
For some reason, I am no longer able to interact with my development database at all anymore.
I've tried rake db:create, and it makes my test database fine, but the dev one is not created at all.
I'm using the postgresapp.com, and up until just recently, it was working flawlessly. No changes to my config/database.yml file have been made recently, nor to any of my app config files.
I can connect to my test database fine with psql -h localhost redtail_test, and it uses the same connection credentials as my dev box, so I'm reasonably sure it's not a connection issue with PG--unless it's a weird one.
redtail git:master ❯ rake db:create
redtail_test already exists
redtail git:master ❯ psql -h localhost redtail
psql: FATAL: database "redtail" does not exist
Has anyone ran into this issue?
common: &common
encoding: utf8
postgres: &postgres
adapter: postgresql
user: postgres
password:
min_messages: WARNING
development: &development
<<: *common
<<: *postgres
host: localhost
database: redtail
memory: &memory
<<: *common
adapter: sqlite3
host: localhost
database: ":memory:"
test: &test
<<: *common
<<: *postgres
host: localhost
database: redtail_test
production:
adapter: postgresql
encoding: utf8
database: redtail
cucumber:
<<: *test